simple_launch package from simple_launch reposimple_launch |
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Package Summary
Tags | No category tags. |
Version | 1.10.1 |
License | MIT |
Build type | AMENT_CMAKE |
Use | RECOMMENDED |
Repository Summary
Checkout URI | https://github.com/oKermorgant/simple_launch.git |
VCS Type | git |
VCS Version | devel |
Last Updated | 2024-11-21 |
Dev Status | MAINTAINED |
CI status | No Continuous Integration |
Released | RELEASED |
Tags | No category tags. |
Contributing |
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Package Description
Additional Links
Maintainers
- Olivier Kermorgant
Authors
simple_launch
This package provides a Python class to help writing ROS 2 launch files.
The motivation behind this package is that the ROS 2 launch Python syntax may not be suited for many simple cases such as running basic nodes, spawning a robot_state_publisher
, and grouping nodes in namespaces or components.
Thanks: this package is inspired by ros2_launch_util.
The entry point is the SimpleLauncher
class, which has several capabilities.
Basic syntax
Namespace and argument parser initialization
sl = SimpleLauncher(namespace = '', use_sim_time = None, scope_included_files = False)
- will initialize all nodes relative to the given namespace
- if
use_sim_time
is a Boolean, creates ause_sim_time
launch argument with this value as the default and forwards it to all nodes, unless explicitely specified when running the node - if
use_sim_time
is'auto'
, thenSimpleLauncher
will set it toTrue
if the/clock
topic is advertized (case of an already running simulation). This may have side effects if the/clock
topic is advertized but you want to use this launch file with system clock. - if
use_sim_time
isNone
(default) then no particular value is forwarded to the nodes - if
scope_included_files
isFalse
(default) then including another launch file that shares the same argument but while passing another value for this argument, will also modify the value of this argument after the inclusion. This is the default behavior oflaunch
but can be undesired. Inside anOpaqueFunction
the behavior is to be scoped anyway (the argument value is resolved) andscope_included_files
has no effect.
Node registration
sl.node(package, executable, **node_args)
where
-
package
is the node package -
executable
is the name of the executable -
node_args
are any additionalNode
arguments
Launch file include
sl.include(package, launch_file, launch_dir = None, launch_arguments=None)
where
-
package
is the package of the included launch file -
launch_file
is the name of the launch file -
launch_dir
is its directory inside the package share (None
to have it found) -
launch_arguments
is a dictionary of arguments to pass to the included launch file
Call a service at launch
This line runs a temporary client that waits for a service and calls it when available:
sl.call_service(server, request = None, verbosity = '')
where
-
server
is the path to some service (possibly namespaced). The service type is deduced when it becomes available. -
request
is a dictionary representing the service request. IfNone
or incomplete, will use the service request default values. -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
If any request parameter is __ns
it will be changed to the current namespace.
Setting parameters
This line runs a temporary client that waits for a node and changes its parameters when available:
sl.set_parameters(node_name, parameters: dict = {}, verbosity = '')
where
-
node_name
is the name of the node (possibly namespaced) -
parameters
is a dictionary of (name, value) parameters to be set -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
This calls the set_parameters
service of the node with the passed types. Possible errors may happen if the parameters do not exist or are of a different type.
Robust types for parameters
In the launch API, differents types are expected for:
- node parameters: a list of dictionaries
- node remappings: a list of (
key
,value
) pairs - included launch arguments: a list of (
key
,value
) pairs - xacro arguments: a concatenation of
key:=value
strings
The sl.include
, sl.node
and xacro_args
calls allow using any type (the simplest being a single dictionary) and will convert to the one expected by the API.
Launch arguments
simple_launch
allows declaring launch arguments and getting them in return.
Declare a launch argument
sl.declare_arg(name, default_value, description = None)
: declare and returns the argument
Contrary to the base API, the default value is a raw Python type.
Retrieve a launch argument
sl.arg(name)
: returns the argument name
as a SimpleSubstitution
Retrieve several arguments as a dictionary
sl.arg_map('robot', 'x', 'y')
: returns {'robot': <robot arg value>, 'x': <x arg value>, 'y': <y arg value>}
Typical when forwarding some launch arguments to a node or an included launch file.
Groups or scopes
Groups are created through the with sl.group():
syntax and accept, a namespace an if/unless condition and an event.
Actions that are added in a scope inherit from all previous defined groups.
By namespace
with sl.group(ns=sub_namespace):
sl.node(package, executable)
From a condition
with sl.group(if_condition=True):
sl.node(package, executable)
with sl.group(unless_condition=<some expression>):
sl.node(package, executable)
- Only one condition can be set in a group, nested condition must be combined first, or used in nested groups.
- Combining conditions coming from launch arguments can be done with
sl.py_eval
as shown below.
From conditional arguments
with sl.group(if_arg='use_gui'):
sl.node(package, executable)
with sl.group(unless_arg='dont_do'):
sl.node(package, executable)
if_arg
/ unless_arg
is expected to be the name of a launch argument. These two lines are equivalent:
with sl.group(if_arg='use_gui'):
with sl.group(if_condition=sl.arg('use_gui')):
If if_arg
/ unless_arg
is not a string then it is considered as a if_condition
/ unless_condition
.
From events
The when
argument wraps events from the launch.event_handlers
module. It combines an event and a delay (0 by default)
from simple_launch.events import When, OnProcessStart, OnProcessExit, OnProcessIO
my_node = sl.node(...) # reference node
with sl.group(when = When(my_node, OnProcessStart, 1.)):
sl.node(...) # will run 1 s after main node starts
with sl.group(when = When(my_node, OnProcessExit)):
sl.node(...) # will run as soon as the main node exists
with sl.group(when = When(my_node, OnProcessIO, io = 'stdout'):
# OnProcessIO events need a function changing the event into an action
sl.add_action(lambda event: LogInfo(msg = 'Node says "{}"'.format(
event.text.decode().strip())))
# several functions can be used if needed, they will be combined in a single one
sl.add_action(lambda event: LogInfo(msg = 'Once again, node says "{}"'.format(
event.text.decode().strip())))
with sl.group(when = When(delay = 2.)):
sl.node(...) # will run after 2 sec
Creating containers
This syntax adds the composition/composition::Talker
as a ComposableNode
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
Use the executable
and package
parameters if you want to use executors other than rclcpp_components
’s component_container
:
with sl.container(name='my_container', output='screen', executable='component_container_isolated'):
It is currently impossible to have group blocks within a container block, as containers can only accept ComposableNode
s. A GroupAction
containing e.g. PushRosNamespace
and a ComposableNode
is not itself a ComposableNode
.
use_sim_time
The current use_sim_time
setting can be retrieved through sl.sim_time
that may be:
-
None
, ifuse_sim_time
was not set in theSimpleLauncher
constructor - a raw Boolean, if
use_sim_time
was set to'auto'
, depending on the/clock
topic being advertized - a Boolean launch argument, if
use_sim_time
was set toTrue
orFalse
In all cases, if the use_sim_time
parameter is explicitely given to a node, it will be used instead of the SimpleLauncher
instance one.
OpaqueFunction
with implicit .perform(context)
Most of the use cases can be dealt with substitutions and with sl.group
blocks.
In order to design more imperative launch files, the OpaqueFunction
approach can be used. The main drawback is that potential errors are harder to track.
To do this with simple_launch
:
- the
SimpleLauncher
instance and the argument declaration should be done in the main body of your launch file. - then, define a function (e.g.
launch_setup
) that takes no argument, where the logic of the launch file resides. - all arguments obtained through
sl.arg
will be basic Python types, obtained from performing the substitutions. - finally just export
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
.
Compare example_launch.py
and example_opaque_launch.py
to see the two approaches on the same logic.
Note that inside an OpaqueFunction
the if/unless idiom reduces to a basic if/else:
# with substitutions
with sl.group(if_arg='some_condition'):
# do stuff
with sl.group(unless_arg='some_condition'):
# do other stuff
# with opaque function
if sl.arg('some_condition'):
# do stuff
else:
# do other stuff
Other one-liners
Methods listed below return instances of SimpleSubstitution
that represent any Substitution, but that provides concatenation (+
) and path concatenation (/
) operators. It is still a Substitution
, not a raw Python type. If run from an OpaqueFunction
the underlying Python variable is returned.
String / substitution concatenation
The following syntax builds the SimpleSubstitution
corresponding to <robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
deprecated: sl.name_join(sl.arg('robot'), '.xacro')
Path concatenation
The following syntax builds the SimpleSubstitution
corresponding to <package_path>/urdf/<robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
urdf_file = os.path.join(get_package_share_directory(package),'urdf')/file_name
Obviously if all the path elements are raw strings, you should use os.path.join
all along.
deprecated: sl.path_join(get_package_share_directory(package), sl.arg('robot'), '.xacro')
Find a share file
path = sl.find(package, file_name = None, file_dir = None)
where:
-
package
is the name of the package orNone
iffile_name
is already an absolute path -
file_name
is the name of the file to find -
file_dir
is the path inside the package
If file_dir
is None
but package
and file_name
are raw strings then the find
function will actually look for the file inside the package share, using os.walk
.
If file_name
is None
then the function just returns the path to the package share directory (e.g. get_package_share_directory(package)
)
Robot state publisher
It is quite common to run a robot_state_publisher
from a urdf
or xacro
file. The line below runs it at the current namespace / condition level:
sl.robot_state_publisher(package, description_file, description_dir=None, xacro_args=None, **node_args)
where
-
description_file
is a URDF or xacro file -
description_dir
is the sub-directory of the file. If omitted, let the script search for the file assuming it is a raw string -
xacro_args
is a dictionary of arguments to forward to xacro -
node_args
are any additional arguments forrobot_state_publisher
(remappings / parameters)
Python expressions
sl.py_eval
will evaluate the given arguments as a Python expression, possibly performed if in an Opaque Function.
# RGB color as a list of [0-255] integers
sl.declare_arg('color', [255,0,0])
# same color as a string of [0-1] numbers (URDF format), note the padding commas to get a string
xacro_color = "'" + sl.py_eval("' '.join(str(c/255) for c in ", sl.arg('color'), ')') + "'"
Conditions
sl.py_eval
can be used to combine conditions. It is robust to lower case true
or false
and will return a SimpleSubstitution
.
sl.declare_arg('some_condition', True)
opposed = sl.py_eval('not ', sl.arg('some_condition'))
Note that IfCondition
and UnlessCondition
cannot be combined, only the underlying Substitution
s can.
Joint state publisher
sl.joint_state_publisher(use_gui, **node_args)
: fires up a joint_state_publisher
, with or without the gui, in the current namespace.
Rviz
sl.rviz(config_file = None, warnings = False)
: runs RViz on the given configuration file. If warnings
is False
(default) then runs with log-level FATAL
in order to avoid many messages in the console.
Classical use case: sl.rviz(sl.find('my_package', 'some_rviz_config.rviz'))
Fallback to low-level syntax
If any unavailable functionality is needed, the sl.add_action(action)
function adds any passed Action
at the current namespace / conditional / event level.
Interaction with Gazebo / Ignition
Note: Ignition being renamed to Gazebo, all tools in this section use Gazebo / gz names
An effort was made to be robust to Ignition versus Gazebo uses, i.e. ign prefix is used for foxy
and galactic
while gz prefix is used from humble
. GZ_VERSION
and IGNITION_VERSION
environment variables are also used to identify which version should be preferred.
Launch Gazebo
The Gazebo launch file corresponding to the current ROS 2 distribution is launched with
sl.gz_launch(world_file, gz_arguments)
Namely, it will redirect to either ros_ign_gazebo/ign_gazebo.launch.py
(foxy
, galactic
) or ros_gz_sim/gz_sim.launch.py
(humble
+).
The given gz_arguments
, if any, will be forwarded either as the ign_args
or gz_args
, accordingly.
If the world file can be parsed then SimpleLaunch
will detect its name and forward it to GazeboBridge
functions.
Spawn a model
The following function allows easily spawing a model from its robot_description
:
sl.spawn_gz_model(name, topic, model_file = None, spawn_args = [], only_new = True)
-
name
is the name this model will get in Gazebo -
topic
is the topic to obtain the model from, default isrobot_description
(relative to the current namespace) -
model_file
is the path to the (urdf or sdf) file. If defined then this will spawn this model and ignore the topic -
only_new
if True, will not spawn the model if it already exists in a running Gazebo instance -
spawn_args
are any additional spawn arguments, e.g. the initial pose
example: sl.spawn_gz_model('my_robot', model_file = sl.find('my_pkg', 'my_model.urdf'))
Declare initial pose
Calling sl.declare_gazebo_axes()
will declare all 6 parameters (x,y,z,roll,pitch,yaw)
with 0
as default values.
If any axis is given (e.g. sl.declare_gazebo_axes(yaw = 3.14)
then only this parameter will be declared.
Such parameters can be retrieved through sl.gazebo_axes_args()
. As a consequence, it is easy to spawn a model with:
sl.declare_gazebo_axes()
sl.robot_description(...)
sl.spawn_gz_model(name, spawn_args = sl.gazebo_axes_args())
Save current world
If the simulation is reset after some models have been spawned, they will disappear. A convenient way to avoid this is to generate the full SDF world from a running simulation. The Gazebo GUI is able to export the current world but cannot resolve models that were spawned from e.g. a robot_description
topic.
The script generate_gz_world
will generate a SDF corresponding to the current simulation. If some models have been spawned from URDF and topics, the script will get the corresponding description and insert it into the SDF, assuming robot name
has its description under /name/robot_description
. It can also be called from a launch file with (see Gazebo example):
# you might want to add a delay to be sure all models have been spawned
sl.save_gz_world(full_world.sdf, after = 1.)
Such a self-contained SDF world file is then compatible with a reset of the simulation. See Gazebo example for launch file that checks if the full world is available.
Gazebo bridge
The GazeboBridge
class allows easily creating bridges when using Gazebo.
An instance is created with: bridge = GazeboBridge(<gazebo_topic>, <ros_topic>, <ros_message>, direction, <gz_message> = None)
where direction
is either:
-
GazeboBridge.gz2ros
for Gazebo -> ROS -
GazeboBridge.ros2gz
for ROS -> Gazebo -
GazeboBridge.bidirectional
for both
The Gazebo message type is deduced from the ROS message type if not set. Remapping will be set to the given ros_topic
.
The SimpleLauncher instance can then run a node dealing with declared bridges, as illustrated in the examples at this end of this document.
sl.create_gz_bridge([bridges], <node_name>)
If some bridges involve sensor_msgs/Image
then a dedicated ros_gz_image
bridge will be used. The corresponding camera_info
topic will be also bridged.
Interaction with Gazebo sim
Some bridges (e.g. joint_states
) need to have information on the world name. This name can only be obtained while Gazebo is running, or by having a priori knowledge of the world file.
The GazeboBridge
class has a few static methods to get information on the simulated world, namely:
-
GazeboBridge.world()
returns the current world name -
GazeboBridge.set_world_name(world)
imposes the world name -
GazeboBridge.model_prefix(model)
builds the Gazebo topic relative to the given model/world/<world>/model/<model>
They can be used under these conditions:
-
sl.gz_launch
was called first (in the same launch setup) and the world file could be parsed, in this case the world name from the file is used - or
GazeboBridge.set_world_name(world)
was called first (in the same launch setup), in this case this world name is used - if none of the above and a running Gazebo instance exists, in this case
GazeboBridge
will request information on the world
If none of these conditions hold, the launch file will not be able to get information on the world, and launch fill probably fail.
Built-in bridges
A common instance of the bridge is the clock. This one can be:
- created with
GazeboBridge.clock()
: returns aGazeboBridge
instance, not added to any node yet - or run directly with
sl.create_gz_clock_bridge()
(actually runssl.create_gz_bridge(GazeboBridge.clock())
)
Another common but tedious bridge instance is the joint state topic of a given model. This topic includes, in Gazebo, the name of the world and of the model. Assuming the world name is known, the corresponding bridge can be created with:
GazeboBridge.joint_states_bridge(model)
- actually runs
GazeboBridge('/world/<world>/model/<model>/joint_state', 'joint_states', 'sensor_msgs/JointState', GazeboBridge.gz2ros)
World TF publisher
If /tf
is used with Gazebo, then the root frame used by Gazebo depends on the world name. This frame is usually world
on the ROS side.
A trivial static_transform_publisher
is run to connect these two frames if they have different names:
-
sl.gz_world_tf(world_frame = None)
: run astatic_transform_publisher
fromworld
toworld_frame
. IfNone
then detect the one currently used by Gazebo.
Examples
Examples can be found in the corresponding folder.
Launch with arguments
Here is a file spawning a robot_state_publisher
and its joint_state_publisher
, where:
-
prefix
,x
andy
are launch arguments that are passed to xacro -
use_gui
tells whetherjoint_state_publisher
should run the gui
from simple_launch import SimpleLauncher
def generate_launch_description():
'''
Launch description for a single robot - runs the two nodes in their own namespace
'''
sl = SimpleLauncher()
sl.declare_arg('prefix', default_value = '', description='name of the robot (+ tf prefix)')
sl.declare_arg('x', default_value = 0, description='x-offset of the robot')
sl.declare_arg('y', default_value = 0, description='y-offset of the robot')
sl.declare_arg('use_gui', default_value = True, description='Use JSP gui')
xacro_args = sl.arg_map('prefix', 'x', 'y')
xacro_args['prefix'] += '/' # can sum substitutions and strings
with sl.group(ns=sl.arg('prefix')):
sl.robot_state_publisher('simple_launch', 'turret.xacro', xacro_args = xacro_args)
sl.joint_state_publisher(use_gui = sl.arg('use_gui'))
return sl.launch_description()
Conditional blocks and includes
The file below fires up either robot1
or robot2
(or both) and also has a boolean argument to spawn RViz2
:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
with sl.group(if_arg='robot1'):
sl.include('simple_launch', 'included_launch.py',
launch_arguments = {'prefix': 'robot1'})
with sl.group(if_arg='robot2'):
with sl.group(unless_arg='no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
sl.include('simple_launch', 'included_launch.py', launch_arguments=args)
with sl.group(if_arg='rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
Conditions with OpaqueFunction
The file below does the same as the previous one, but using an OpaqueFunction
:
from simple_launch import SimpleLauncher
# declare simple launcher and the launch arguments in the main body
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
# string args
sl.declare_arg('included', default_value = 'included_launch')
# define the opaque function, context will be wrapped in the SimpleLauncher instance
def launch_setup():
# we can use raw if as `robot1` argument is performed to a Boolean
if sl.arg('robot1'):
sl.include('simple_launch', 'included_launch.py', launch_arguments = {'prefix': 'robot1'})
# and even combine conditions
if sl.arg('robot2') and not sl.arg('no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
# summing up args and strings
sl.include('simple_launch', sl.arg('included') + '.py', launch_arguments=args)
if sl.arg('rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
# tell SimpleLauncher to rely on the opaque_function in the launch description
# /!\ no `def generate_launch_description():`
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
Combining conditions
The file below shows how to use sl.py_eval
to combine conditions. We have to build a valid Python expression, not forgetting the spaces around and
, or
, not
, etc.
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
cond1 = sl.declare_arg('cond1', True)
cond2 = sl.declare_arg('cond2', False)
for logic in ('and', 'or'):
# builds <cond1> <logic> <cond2> Python expression
combined = sl.py_eval(cond1, f' {logic} ', cond2)
sl.log_info([f'{logic} condition is ', combined])
with sl.group(if_condition = combined):
sl.node('demo_nodes_cpp', 'talker', name = f'talker_{logic}')
# also works with sl.node(..., condition = IfCondition(combined))
return sl.launch_description()
Composition
The file below is another way to write the composition launch example:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
sl.node(package='composition', plugin='Listener', name='listener')
return sl.launch_description()
Events and parameters
This example file is another way to write the event launch example. If does a little more work and is a little smarter, as the passed new_background_r
is applied as soon as it has a valid value.
auto sim time
Here we run Gazebo and force all other nodes to use_sim_time:=True
, unless this file is included from another one with use_sim_time:=False
.
This is unlikely as this launch file spawns a simulator.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
# all nodes in this launch file will use_sim_time:=True
sl = SimpleLauncher(use_sim_time=True)
# run Gazebo + clock bridge
sl.gz_launch(<path/to/some/sdf/world>, '-r')
sl.create_gz_clock_bridge()
# run other nodes with sim time
return sl.launch_description()
Robot description and conditionnal Gazebo bridge
The file below only runs by default a robot_state_publisher
with use_sim_time:=False
.
However, if it is included from another file with use_sim_time:=True
then it also spawns the robot into Gazebo and runs two bridges for joint states and pose.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
sl = SimpleLauncher(use_sim_time=False)
# namespace is a launch argument, not a Python string
sl.declare_arg('robot', default_value = 'robot1')
robot = sl.arg('robot')
with sl.group(ns = robot):
# robot_state_publisher is always run
sl.robot_state_publisher('my_description', 'my_robot.xacro')
with sl.group(if_condition = sl.sim_time):
# only execute this group if use_sim_time was set to True
# spawn in Gazebo at default pose if not already here
sl.spawn_gz_model(robot)
# create a bridge for joint states @ /world/<world>/model/<robot>/joint_state
# note the relative ROS topic 'joint_states' that is actually namespaced
gz_js_topic = GazeboBridge.model_prefix(robot)/'joint_state'
js_bridge = GazeboBridge(gz_topic = gz_js_topic,
ros_topic = 'joint_states',
msg = 'sensor_msgs/JointState',
direction = GazeboBridge.gz2ros)
# pose publisher bridge @ /model/<robot>
pose_bridge = GazeboBridge('/model'/robot/'/pose',
'pose_gt', 'geometry_msgs/Pose', GazeboBridge.gz2ros)
# create bridge node with these two topics with default name gz_bridge
sl.create_gz_bridge([js_bridge, pose_bridge])
return sl.launch_description()
Full Gazebo simulation
The file example/gazebo/gazebo_launch.py
runs a basic simulation of a turret robot with a camera, also displayed in RViz.
ros2 launch simple_launch gazebo_launch.py
You can move the robot around with a joint velocity setpoint (std_msgs/Float64
) on /turret/joint#
and see the simulated camera on /turret/image
.
I want more examples
Other self-contained examples (and slides) have been used to teach the ROS 2 launch file system and the nav stack.
Various aspects of the launch systen are shown in the anf_launch package.
A simple tutorial on Nav2
using simple_launch
is available in the anf_nav package.
Changelog for package simple_launch
1.10.1 (2024-07-05)
- check for gz/ign executable being available
- gz_world_tf + better guess on Gz vs Ign
- Contributors: Olivier Kermorgant
1.10.0 (2024-06-16)
- scope_included_files to include other launch files in a Group and avoid changing my scope
- remove dead code about prefixing gz plugins
- forward sim_time even for nodes that load a parameter file
- lazy GazeboBridge
- Contributors: Olivier Kermorgant
1.9.2 (2024-03-25)
- Gazebo basic example: launch SDF world + spawn from xacro
- remove dead code related to Gazebo.
- sl.arg returns a SimpleSubstitution to allow concatenation
- auto-detect Gazebo world name, allows running the simulation + spawn models in the same launch file
- Type debug on String being Iterable
- better handling of non-string choices in argument declaration
- more robust to various gz/ros combinations
- Contributors: Olivier Kermorgant
1.9.1 (2024-02-20)
- simplify + debug logic of SimpleSubstitution divisions
- image instead of /image to be detected as an image topic
- remove auto_sim_time function
- more robust to various combinations of ROS and Gazebo
- default Gazebo is still ignition Fortress, better error message about GZ_VERSION
- add new bridges for Gazebo
- Contributors: Olivier Kermorgant
1.9.0 (2023-11-23)
- update documentation
- warnings/errors on misuse of GazeboBridge
- move example executable to share directory
- dict cannot be updated with | in Foxy, fallback to dict.update
- absolute container name when loading in existing container
- py_eval can now handle conditions
- Contributors: Olivier Kermorgant
1.8.0 (2023-11-20)
- sync documentation and examples
- when instead of after for events
- scoped events
- add event wrapper
- Contributors: Olivier Kermorgant
1.7.2 (2023-10-02)
- simplify logic of try_perform
- Merge pull request #5 from okvik/devel Fix string-valued launch argument substitution
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant, Viktor Pocedulic
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant
1.7.1 (2023-05-16)
- list[] -> List[] for type hints in 20.04
- detail on __ns for services
- add service call at launch
- Contributors: Olivier Kermorgant
1.7.0 (2023-02-22)
- GazeboBridge creates a camera_info topic for all bridged image topics
- Contributors: Olivier Kermorgant
1.6.2 (2023-01-23)
- add .rviz shortcut, clean Python scripts
- Contributors: Olivier Kermorgant
1.6.1 (2022-10-10)
- fix bug in robot_state_publisher with raw URDF
- Contributors: Olivier Kermorgant
1.6.0 (2022-10-06)
- check use_sim_time versus a parameter file
- resolve any builtin type as Substitution, not only text
- improve documentation
- Gazebo + humble compat
- OpaqueFunction wrapper and SimpleSubstitution
- switch to CMake to avoid deprecation messages
- more spawn_gz
- Contributors: Olivier Kermorgant
1.5.0 (2022-08-26)
- allow spawning a Gz model from file
- parameters are list of dict
- allow substitution for topics in ros_ign_image bridge
- Gazebo bridge handles invalid ROS topics through yaml config file. Image bridges are automatically run through ros_ign_image
- better handling of gazebo spawn pose
- Contributors: Olivier Kermorgant
1.4.1 (2022-06-01)
- more handling of param types
- Contributors: Olivier Kermorgant
1.4.0 (2022-06-01)
- use Gazebo instead of Ignition
- better type comprehension
- Contributors: Olivier Kermorgant
1.3.1 (2022-05-02)
- use underscores in setup.cfg
- typo in included_launch example
- Merge pull request #4 from yushijinhun/patch-1 Add package & executable parameter to container
- [readme] add doc for container.package
- Add package & executable param to container This allows the user to use a component container implementation other than [component_container]{.title-ref}, such as [component_container_isolated]{.title-ref} and [component_container_mt]{.title-ref}.
- Contributors: Haowei Wen, Olivier Kermorgant
1.3.0 (2022-02-03)
- more use_sim_time: constructor + warning on 'auto'
- auto_sim_time can be forced instead of checking /clock
- Contributors: Olivier Kermorgant
1.2.1 (2022-01-24)
- add Ignition support
- Contributors: Olivier Kermorgant
1.2.0 (2021-11-02)
- make it clearer for the prefix_gz_plugins param
- Contributors: Olivier Kermorgant
1.1.0 (2021-09-25)
- add capacity to prefix and namespace Gazebo-published messages, as an alternative to using Gazebo namespaces that also remap /tf
- Contributors: Olivier Kermorgant
1.0.6 (2021-09-22)
- node arguments is a raw list and accepts substitutions
- Contributors: Olivier Kermorgant
1.0.5 (2021-09-22)
- automagically convert to expected type for node parameters, remappings, launch arguments
- Contributors: Olivier Kermorgant
1.0.4 (2021-09-03)
- some Python2 legacy bugs
- Contributors: Olivier Kermorgant
1.0.3 (2021-04-17)
- solve typo in node_args
- better handling of node arguments in nested lists
- bug fixes around Substitutions
- Merge pull request #1 from oKermorgant/master deduce executable from package name if needed
- Contributors: Olivier Kermorgant
1.0.2 (2020-12-08)
- composition with existing container
- Contributors: Olivier Kermorgant
1.0.1 (2020-10-12)
- PythonExpression shortcut
- xacro args now take substitution args
- add LoadComposableNode feature for existing containers
- add name_join and path_join to combine raw str and Substitution stuff
- first commit
- Contributors: Olivier Kermorgant
Wiki Tutorials
Package Dependencies
System Dependencies
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Services
Plugins
Recent questions tagged simple_launch at Robotics Stack Exchange
simple_launch package from simple_launch reposimple_launch |
|
Package Summary
Tags | No category tags. |
Version | 1.10.1 |
License | MIT |
Build type | AMENT_CMAKE |
Use | RECOMMENDED |
Repository Summary
Checkout URI | https://github.com/oKermorgant/simple_launch.git |
VCS Type | git |
VCS Version | devel |
Last Updated | 2024-11-21 |
Dev Status | MAINTAINED |
CI status | No Continuous Integration |
Released | RELEASED |
Tags | No category tags. |
Contributing |
Help Wanted (0)
Good First Issues (0) Pull Requests to Review (0) |
Package Description
Additional Links
Maintainers
- Olivier Kermorgant
Authors
simple_launch
This package provides a Python class to help writing ROS 2 launch files.
The motivation behind this package is that the ROS 2 launch Python syntax may not be suited for many simple cases such as running basic nodes, spawning a robot_state_publisher
, and grouping nodes in namespaces or components.
Thanks: this package is inspired by ros2_launch_util.
The entry point is the SimpleLauncher
class, which has several capabilities.
Basic syntax
Namespace and argument parser initialization
sl = SimpleLauncher(namespace = '', use_sim_time = None, scope_included_files = False)
- will initialize all nodes relative to the given namespace
- if
use_sim_time
is a Boolean, creates ause_sim_time
launch argument with this value as the default and forwards it to all nodes, unless explicitely specified when running the node - if
use_sim_time
is'auto'
, thenSimpleLauncher
will set it toTrue
if the/clock
topic is advertized (case of an already running simulation). This may have side effects if the/clock
topic is advertized but you want to use this launch file with system clock. - if
use_sim_time
isNone
(default) then no particular value is forwarded to the nodes - if
scope_included_files
isFalse
(default) then including another launch file that shares the same argument but while passing another value for this argument, will also modify the value of this argument after the inclusion. This is the default behavior oflaunch
but can be undesired. Inside anOpaqueFunction
the behavior is to be scoped anyway (the argument value is resolved) andscope_included_files
has no effect.
Node registration
sl.node(package, executable, **node_args)
where
-
package
is the node package -
executable
is the name of the executable -
node_args
are any additionalNode
arguments
Launch file include
sl.include(package, launch_file, launch_dir = None, launch_arguments=None)
where
-
package
is the package of the included launch file -
launch_file
is the name of the launch file -
launch_dir
is its directory inside the package share (None
to have it found) -
launch_arguments
is a dictionary of arguments to pass to the included launch file
Call a service at launch
This line runs a temporary client that waits for a service and calls it when available:
sl.call_service(server, request = None, verbosity = '')
where
-
server
is the path to some service (possibly namespaced). The service type is deduced when it becomes available. -
request
is a dictionary representing the service request. IfNone
or incomplete, will use the service request default values. -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
If any request parameter is __ns
it will be changed to the current namespace.
Setting parameters
This line runs a temporary client that waits for a node and changes its parameters when available:
sl.set_parameters(node_name, parameters: dict = {}, verbosity = '')
where
-
node_name
is the name of the node (possibly namespaced) -
parameters
is a dictionary of (name, value) parameters to be set -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
This calls the set_parameters
service of the node with the passed types. Possible errors may happen if the parameters do not exist or are of a different type.
Robust types for parameters
In the launch API, differents types are expected for:
- node parameters: a list of dictionaries
- node remappings: a list of (
key
,value
) pairs - included launch arguments: a list of (
key
,value
) pairs - xacro arguments: a concatenation of
key:=value
strings
The sl.include
, sl.node
and xacro_args
calls allow using any type (the simplest being a single dictionary) and will convert to the one expected by the API.
Launch arguments
simple_launch
allows declaring launch arguments and getting them in return.
Declare a launch argument
sl.declare_arg(name, default_value, description = None)
: declare and returns the argument
Contrary to the base API, the default value is a raw Python type.
Retrieve a launch argument
sl.arg(name)
: returns the argument name
as a SimpleSubstitution
Retrieve several arguments as a dictionary
sl.arg_map('robot', 'x', 'y')
: returns {'robot': <robot arg value>, 'x': <x arg value>, 'y': <y arg value>}
Typical when forwarding some launch arguments to a node or an included launch file.
Groups or scopes
Groups are created through the with sl.group():
syntax and accept, a namespace an if/unless condition and an event.
Actions that are added in a scope inherit from all previous defined groups.
By namespace
with sl.group(ns=sub_namespace):
sl.node(package, executable)
From a condition
with sl.group(if_condition=True):
sl.node(package, executable)
with sl.group(unless_condition=<some expression>):
sl.node(package, executable)
- Only one condition can be set in a group, nested condition must be combined first, or used in nested groups.
- Combining conditions coming from launch arguments can be done with
sl.py_eval
as shown below.
From conditional arguments
with sl.group(if_arg='use_gui'):
sl.node(package, executable)
with sl.group(unless_arg='dont_do'):
sl.node(package, executable)
if_arg
/ unless_arg
is expected to be the name of a launch argument. These two lines are equivalent:
with sl.group(if_arg='use_gui'):
with sl.group(if_condition=sl.arg('use_gui')):
If if_arg
/ unless_arg
is not a string then it is considered as a if_condition
/ unless_condition
.
From events
The when
argument wraps events from the launch.event_handlers
module. It combines an event and a delay (0 by default)
from simple_launch.events import When, OnProcessStart, OnProcessExit, OnProcessIO
my_node = sl.node(...) # reference node
with sl.group(when = When(my_node, OnProcessStart, 1.)):
sl.node(...) # will run 1 s after main node starts
with sl.group(when = When(my_node, OnProcessExit)):
sl.node(...) # will run as soon as the main node exists
with sl.group(when = When(my_node, OnProcessIO, io = 'stdout'):
# OnProcessIO events need a function changing the event into an action
sl.add_action(lambda event: LogInfo(msg = 'Node says "{}"'.format(
event.text.decode().strip())))
# several functions can be used if needed, they will be combined in a single one
sl.add_action(lambda event: LogInfo(msg = 'Once again, node says "{}"'.format(
event.text.decode().strip())))
with sl.group(when = When(delay = 2.)):
sl.node(...) # will run after 2 sec
Creating containers
This syntax adds the composition/composition::Talker
as a ComposableNode
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
Use the executable
and package
parameters if you want to use executors other than rclcpp_components
’s component_container
:
with sl.container(name='my_container', output='screen', executable='component_container_isolated'):
It is currently impossible to have group blocks within a container block, as containers can only accept ComposableNode
s. A GroupAction
containing e.g. PushRosNamespace
and a ComposableNode
is not itself a ComposableNode
.
use_sim_time
The current use_sim_time
setting can be retrieved through sl.sim_time
that may be:
-
None
, ifuse_sim_time
was not set in theSimpleLauncher
constructor - a raw Boolean, if
use_sim_time
was set to'auto'
, depending on the/clock
topic being advertized - a Boolean launch argument, if
use_sim_time
was set toTrue
orFalse
In all cases, if the use_sim_time
parameter is explicitely given to a node, it will be used instead of the SimpleLauncher
instance one.
OpaqueFunction
with implicit .perform(context)
Most of the use cases can be dealt with substitutions and with sl.group
blocks.
In order to design more imperative launch files, the OpaqueFunction
approach can be used. The main drawback is that potential errors are harder to track.
To do this with simple_launch
:
- the
SimpleLauncher
instance and the argument declaration should be done in the main body of your launch file. - then, define a function (e.g.
launch_setup
) that takes no argument, where the logic of the launch file resides. - all arguments obtained through
sl.arg
will be basic Python types, obtained from performing the substitutions. - finally just export
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
.
Compare example_launch.py
and example_opaque_launch.py
to see the two approaches on the same logic.
Note that inside an OpaqueFunction
the if/unless idiom reduces to a basic if/else:
# with substitutions
with sl.group(if_arg='some_condition'):
# do stuff
with sl.group(unless_arg='some_condition'):
# do other stuff
# with opaque function
if sl.arg('some_condition'):
# do stuff
else:
# do other stuff
Other one-liners
Methods listed below return instances of SimpleSubstitution
that represent any Substitution, but that provides concatenation (+
) and path concatenation (/
) operators. It is still a Substitution
, not a raw Python type. If run from an OpaqueFunction
the underlying Python variable is returned.
String / substitution concatenation
The following syntax builds the SimpleSubstitution
corresponding to <robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
deprecated: sl.name_join(sl.arg('robot'), '.xacro')
Path concatenation
The following syntax builds the SimpleSubstitution
corresponding to <package_path>/urdf/<robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
urdf_file = os.path.join(get_package_share_directory(package),'urdf')/file_name
Obviously if all the path elements are raw strings, you should use os.path.join
all along.
deprecated: sl.path_join(get_package_share_directory(package), sl.arg('robot'), '.xacro')
Find a share file
path = sl.find(package, file_name = None, file_dir = None)
where:
-
package
is the name of the package orNone
iffile_name
is already an absolute path -
file_name
is the name of the file to find -
file_dir
is the path inside the package
If file_dir
is None
but package
and file_name
are raw strings then the find
function will actually look for the file inside the package share, using os.walk
.
If file_name
is None
then the function just returns the path to the package share directory (e.g. get_package_share_directory(package)
)
Robot state publisher
It is quite common to run a robot_state_publisher
from a urdf
or xacro
file. The line below runs it at the current namespace / condition level:
sl.robot_state_publisher(package, description_file, description_dir=None, xacro_args=None, **node_args)
where
-
description_file
is a URDF or xacro file -
description_dir
is the sub-directory of the file. If omitted, let the script search for the file assuming it is a raw string -
xacro_args
is a dictionary of arguments to forward to xacro -
node_args
are any additional arguments forrobot_state_publisher
(remappings / parameters)
Python expressions
sl.py_eval
will evaluate the given arguments as a Python expression, possibly performed if in an Opaque Function.
# RGB color as a list of [0-255] integers
sl.declare_arg('color', [255,0,0])
# same color as a string of [0-1] numbers (URDF format), note the padding commas to get a string
xacro_color = "'" + sl.py_eval("' '.join(str(c/255) for c in ", sl.arg('color'), ')') + "'"
Conditions
sl.py_eval
can be used to combine conditions. It is robust to lower case true
or false
and will return a SimpleSubstitution
.
sl.declare_arg('some_condition', True)
opposed = sl.py_eval('not ', sl.arg('some_condition'))
Note that IfCondition
and UnlessCondition
cannot be combined, only the underlying Substitution
s can.
Joint state publisher
sl.joint_state_publisher(use_gui, **node_args)
: fires up a joint_state_publisher
, with or without the gui, in the current namespace.
Rviz
sl.rviz(config_file = None, warnings = False)
: runs RViz on the given configuration file. If warnings
is False
(default) then runs with log-level FATAL
in order to avoid many messages in the console.
Classical use case: sl.rviz(sl.find('my_package', 'some_rviz_config.rviz'))
Fallback to low-level syntax
If any unavailable functionality is needed, the sl.add_action(action)
function adds any passed Action
at the current namespace / conditional / event level.
Interaction with Gazebo / Ignition
Note: Ignition being renamed to Gazebo, all tools in this section use Gazebo / gz names
An effort was made to be robust to Ignition versus Gazebo uses, i.e. ign prefix is used for foxy
and galactic
while gz prefix is used from humble
. GZ_VERSION
and IGNITION_VERSION
environment variables are also used to identify which version should be preferred.
Launch Gazebo
The Gazebo launch file corresponding to the current ROS 2 distribution is launched with
sl.gz_launch(world_file, gz_arguments)
Namely, it will redirect to either ros_ign_gazebo/ign_gazebo.launch.py
(foxy
, galactic
) or ros_gz_sim/gz_sim.launch.py
(humble
+).
The given gz_arguments
, if any, will be forwarded either as the ign_args
or gz_args
, accordingly.
If the world file can be parsed then SimpleLaunch
will detect its name and forward it to GazeboBridge
functions.
Spawn a model
The following function allows easily spawing a model from its robot_description
:
sl.spawn_gz_model(name, topic, model_file = None, spawn_args = [], only_new = True)
-
name
is the name this model will get in Gazebo -
topic
is the topic to obtain the model from, default isrobot_description
(relative to the current namespace) -
model_file
is the path to the (urdf or sdf) file. If defined then this will spawn this model and ignore the topic -
only_new
if True, will not spawn the model if it already exists in a running Gazebo instance -
spawn_args
are any additional spawn arguments, e.g. the initial pose
example: sl.spawn_gz_model('my_robot', model_file = sl.find('my_pkg', 'my_model.urdf'))
Declare initial pose
Calling sl.declare_gazebo_axes()
will declare all 6 parameters (x,y,z,roll,pitch,yaw)
with 0
as default values.
If any axis is given (e.g. sl.declare_gazebo_axes(yaw = 3.14)
then only this parameter will be declared.
Such parameters can be retrieved through sl.gazebo_axes_args()
. As a consequence, it is easy to spawn a model with:
sl.declare_gazebo_axes()
sl.robot_description(...)
sl.spawn_gz_model(name, spawn_args = sl.gazebo_axes_args())
Save current world
If the simulation is reset after some models have been spawned, they will disappear. A convenient way to avoid this is to generate the full SDF world from a running simulation. The Gazebo GUI is able to export the current world but cannot resolve models that were spawned from e.g. a robot_description
topic.
The script generate_gz_world
will generate a SDF corresponding to the current simulation. If some models have been spawned from URDF and topics, the script will get the corresponding description and insert it into the SDF, assuming robot name
has its description under /name/robot_description
. It can also be called from a launch file with (see Gazebo example):
# you might want to add a delay to be sure all models have been spawned
sl.save_gz_world(full_world.sdf, after = 1.)
Such a self-contained SDF world file is then compatible with a reset of the simulation. See Gazebo example for launch file that checks if the full world is available.
Gazebo bridge
The GazeboBridge
class allows easily creating bridges when using Gazebo.
An instance is created with: bridge = GazeboBridge(<gazebo_topic>, <ros_topic>, <ros_message>, direction, <gz_message> = None)
where direction
is either:
-
GazeboBridge.gz2ros
for Gazebo -> ROS -
GazeboBridge.ros2gz
for ROS -> Gazebo -
GazeboBridge.bidirectional
for both
The Gazebo message type is deduced from the ROS message type if not set. Remapping will be set to the given ros_topic
.
The SimpleLauncher instance can then run a node dealing with declared bridges, as illustrated in the examples at this end of this document.
sl.create_gz_bridge([bridges], <node_name>)
If some bridges involve sensor_msgs/Image
then a dedicated ros_gz_image
bridge will be used. The corresponding camera_info
topic will be also bridged.
Interaction with Gazebo sim
Some bridges (e.g. joint_states
) need to have information on the world name. This name can only be obtained while Gazebo is running, or by having a priori knowledge of the world file.
The GazeboBridge
class has a few static methods to get information on the simulated world, namely:
-
GazeboBridge.world()
returns the current world name -
GazeboBridge.set_world_name(world)
imposes the world name -
GazeboBridge.model_prefix(model)
builds the Gazebo topic relative to the given model/world/<world>/model/<model>
They can be used under these conditions:
-
sl.gz_launch
was called first (in the same launch setup) and the world file could be parsed, in this case the world name from the file is used - or
GazeboBridge.set_world_name(world)
was called first (in the same launch setup), in this case this world name is used - if none of the above and a running Gazebo instance exists, in this case
GazeboBridge
will request information on the world
If none of these conditions hold, the launch file will not be able to get information on the world, and launch fill probably fail.
Built-in bridges
A common instance of the bridge is the clock. This one can be:
- created with
GazeboBridge.clock()
: returns aGazeboBridge
instance, not added to any node yet - or run directly with
sl.create_gz_clock_bridge()
(actually runssl.create_gz_bridge(GazeboBridge.clock())
)
Another common but tedious bridge instance is the joint state topic of a given model. This topic includes, in Gazebo, the name of the world and of the model. Assuming the world name is known, the corresponding bridge can be created with:
GazeboBridge.joint_states_bridge(model)
- actually runs
GazeboBridge('/world/<world>/model/<model>/joint_state', 'joint_states', 'sensor_msgs/JointState', GazeboBridge.gz2ros)
World TF publisher
If /tf
is used with Gazebo, then the root frame used by Gazebo depends on the world name. This frame is usually world
on the ROS side.
A trivial static_transform_publisher
is run to connect these two frames if they have different names:
-
sl.gz_world_tf(world_frame = None)
: run astatic_transform_publisher
fromworld
toworld_frame
. IfNone
then detect the one currently used by Gazebo.
Examples
Examples can be found in the corresponding folder.
Launch with arguments
Here is a file spawning a robot_state_publisher
and its joint_state_publisher
, where:
-
prefix
,x
andy
are launch arguments that are passed to xacro -
use_gui
tells whetherjoint_state_publisher
should run the gui
from simple_launch import SimpleLauncher
def generate_launch_description():
'''
Launch description for a single robot - runs the two nodes in their own namespace
'''
sl = SimpleLauncher()
sl.declare_arg('prefix', default_value = '', description='name of the robot (+ tf prefix)')
sl.declare_arg('x', default_value = 0, description='x-offset of the robot')
sl.declare_arg('y', default_value = 0, description='y-offset of the robot')
sl.declare_arg('use_gui', default_value = True, description='Use JSP gui')
xacro_args = sl.arg_map('prefix', 'x', 'y')
xacro_args['prefix'] += '/' # can sum substitutions and strings
with sl.group(ns=sl.arg('prefix')):
sl.robot_state_publisher('simple_launch', 'turret.xacro', xacro_args = xacro_args)
sl.joint_state_publisher(use_gui = sl.arg('use_gui'))
return sl.launch_description()
Conditional blocks and includes
The file below fires up either robot1
or robot2
(or both) and also has a boolean argument to spawn RViz2
:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
with sl.group(if_arg='robot1'):
sl.include('simple_launch', 'included_launch.py',
launch_arguments = {'prefix': 'robot1'})
with sl.group(if_arg='robot2'):
with sl.group(unless_arg='no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
sl.include('simple_launch', 'included_launch.py', launch_arguments=args)
with sl.group(if_arg='rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
Conditions with OpaqueFunction
The file below does the same as the previous one, but using an OpaqueFunction
:
from simple_launch import SimpleLauncher
# declare simple launcher and the launch arguments in the main body
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
# string args
sl.declare_arg('included', default_value = 'included_launch')
# define the opaque function, context will be wrapped in the SimpleLauncher instance
def launch_setup():
# we can use raw if as `robot1` argument is performed to a Boolean
if sl.arg('robot1'):
sl.include('simple_launch', 'included_launch.py', launch_arguments = {'prefix': 'robot1'})
# and even combine conditions
if sl.arg('robot2') and not sl.arg('no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
# summing up args and strings
sl.include('simple_launch', sl.arg('included') + '.py', launch_arguments=args)
if sl.arg('rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
# tell SimpleLauncher to rely on the opaque_function in the launch description
# /!\ no `def generate_launch_description():`
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
Combining conditions
The file below shows how to use sl.py_eval
to combine conditions. We have to build a valid Python expression, not forgetting the spaces around and
, or
, not
, etc.
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
cond1 = sl.declare_arg('cond1', True)
cond2 = sl.declare_arg('cond2', False)
for logic in ('and', 'or'):
# builds <cond1> <logic> <cond2> Python expression
combined = sl.py_eval(cond1, f' {logic} ', cond2)
sl.log_info([f'{logic} condition is ', combined])
with sl.group(if_condition = combined):
sl.node('demo_nodes_cpp', 'talker', name = f'talker_{logic}')
# also works with sl.node(..., condition = IfCondition(combined))
return sl.launch_description()
Composition
The file below is another way to write the composition launch example:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
sl.node(package='composition', plugin='Listener', name='listener')
return sl.launch_description()
Events and parameters
This example file is another way to write the event launch example. If does a little more work and is a little smarter, as the passed new_background_r
is applied as soon as it has a valid value.
auto sim time
Here we run Gazebo and force all other nodes to use_sim_time:=True
, unless this file is included from another one with use_sim_time:=False
.
This is unlikely as this launch file spawns a simulator.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
# all nodes in this launch file will use_sim_time:=True
sl = SimpleLauncher(use_sim_time=True)
# run Gazebo + clock bridge
sl.gz_launch(<path/to/some/sdf/world>, '-r')
sl.create_gz_clock_bridge()
# run other nodes with sim time
return sl.launch_description()
Robot description and conditionnal Gazebo bridge
The file below only runs by default a robot_state_publisher
with use_sim_time:=False
.
However, if it is included from another file with use_sim_time:=True
then it also spawns the robot into Gazebo and runs two bridges for joint states and pose.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
sl = SimpleLauncher(use_sim_time=False)
# namespace is a launch argument, not a Python string
sl.declare_arg('robot', default_value = 'robot1')
robot = sl.arg('robot')
with sl.group(ns = robot):
# robot_state_publisher is always run
sl.robot_state_publisher('my_description', 'my_robot.xacro')
with sl.group(if_condition = sl.sim_time):
# only execute this group if use_sim_time was set to True
# spawn in Gazebo at default pose if not already here
sl.spawn_gz_model(robot)
# create a bridge for joint states @ /world/<world>/model/<robot>/joint_state
# note the relative ROS topic 'joint_states' that is actually namespaced
gz_js_topic = GazeboBridge.model_prefix(robot)/'joint_state'
js_bridge = GazeboBridge(gz_topic = gz_js_topic,
ros_topic = 'joint_states',
msg = 'sensor_msgs/JointState',
direction = GazeboBridge.gz2ros)
# pose publisher bridge @ /model/<robot>
pose_bridge = GazeboBridge('/model'/robot/'/pose',
'pose_gt', 'geometry_msgs/Pose', GazeboBridge.gz2ros)
# create bridge node with these two topics with default name gz_bridge
sl.create_gz_bridge([js_bridge, pose_bridge])
return sl.launch_description()
Full Gazebo simulation
The file example/gazebo/gazebo_launch.py
runs a basic simulation of a turret robot with a camera, also displayed in RViz.
ros2 launch simple_launch gazebo_launch.py
You can move the robot around with a joint velocity setpoint (std_msgs/Float64
) on /turret/joint#
and see the simulated camera on /turret/image
.
I want more examples
Other self-contained examples (and slides) have been used to teach the ROS 2 launch file system and the nav stack.
Various aspects of the launch systen are shown in the anf_launch package.
A simple tutorial on Nav2
using simple_launch
is available in the anf_nav package.
Changelog for package simple_launch
1.10.1 (2024-07-05)
- check for gz/ign executable being available
- gz_world_tf + better guess on Gz vs Ign
- Contributors: Olivier Kermorgant
1.10.0 (2024-06-16)
- scope_included_files to include other launch files in a Group and avoid changing my scope
- remove dead code about prefixing gz plugins
- forward sim_time even for nodes that load a parameter file
- lazy GazeboBridge
- Contributors: Olivier Kermorgant
1.9.2 (2024-03-25)
- Gazebo basic example: launch SDF world + spawn from xacro
- remove dead code related to Gazebo.
- sl.arg returns a SimpleSubstitution to allow concatenation
- auto-detect Gazebo world name, allows running the simulation + spawn models in the same launch file
- Type debug on String being Iterable
- better handling of non-string choices in argument declaration
- more robust to various gz/ros combinations
- Contributors: Olivier Kermorgant
1.9.1 (2024-02-20)
- simplify + debug logic of SimpleSubstitution divisions
- image instead of /image to be detected as an image topic
- remove auto_sim_time function
- more robust to various combinations of ROS and Gazebo
- default Gazebo is still ignition Fortress, better error message about GZ_VERSION
- add new bridges for Gazebo
- Contributors: Olivier Kermorgant
1.9.0 (2023-11-23)
- update documentation
- warnings/errors on misuse of GazeboBridge
- move example executable to share directory
- dict cannot be updated with | in Foxy, fallback to dict.update
- absolute container name when loading in existing container
- py_eval can now handle conditions
- Contributors: Olivier Kermorgant
1.8.0 (2023-11-20)
- sync documentation and examples
- when instead of after for events
- scoped events
- add event wrapper
- Contributors: Olivier Kermorgant
1.7.2 (2023-10-02)
- simplify logic of try_perform
- Merge pull request #5 from okvik/devel Fix string-valued launch argument substitution
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant, Viktor Pocedulic
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant
1.7.1 (2023-05-16)
- list[] -> List[] for type hints in 20.04
- detail on __ns for services
- add service call at launch
- Contributors: Olivier Kermorgant
1.7.0 (2023-02-22)
- GazeboBridge creates a camera_info topic for all bridged image topics
- Contributors: Olivier Kermorgant
1.6.2 (2023-01-23)
- add .rviz shortcut, clean Python scripts
- Contributors: Olivier Kermorgant
1.6.1 (2022-10-10)
- fix bug in robot_state_publisher with raw URDF
- Contributors: Olivier Kermorgant
1.6.0 (2022-10-06)
- check use_sim_time versus a parameter file
- resolve any builtin type as Substitution, not only text
- improve documentation
- Gazebo + humble compat
- OpaqueFunction wrapper and SimpleSubstitution
- switch to CMake to avoid deprecation messages
- more spawn_gz
- Contributors: Olivier Kermorgant
1.5.0 (2022-08-26)
- allow spawning a Gz model from file
- parameters are list of dict
- allow substitution for topics in ros_ign_image bridge
- Gazebo bridge handles invalid ROS topics through yaml config file. Image bridges are automatically run through ros_ign_image
- better handling of gazebo spawn pose
- Contributors: Olivier Kermorgant
1.4.1 (2022-06-01)
- more handling of param types
- Contributors: Olivier Kermorgant
1.4.0 (2022-06-01)
- use Gazebo instead of Ignition
- better type comprehension
- Contributors: Olivier Kermorgant
1.3.1 (2022-05-02)
- use underscores in setup.cfg
- typo in included_launch example
- Merge pull request #4 from yushijinhun/patch-1 Add package & executable parameter to container
- [readme] add doc for container.package
- Add package & executable param to container This allows the user to use a component container implementation other than [component_container]{.title-ref}, such as [component_container_isolated]{.title-ref} and [component_container_mt]{.title-ref}.
- Contributors: Haowei Wen, Olivier Kermorgant
1.3.0 (2022-02-03)
- more use_sim_time: constructor + warning on 'auto'
- auto_sim_time can be forced instead of checking /clock
- Contributors: Olivier Kermorgant
1.2.1 (2022-01-24)
- add Ignition support
- Contributors: Olivier Kermorgant
1.2.0 (2021-11-02)
- make it clearer for the prefix_gz_plugins param
- Contributors: Olivier Kermorgant
1.1.0 (2021-09-25)
- add capacity to prefix and namespace Gazebo-published messages, as an alternative to using Gazebo namespaces that also remap /tf
- Contributors: Olivier Kermorgant
1.0.6 (2021-09-22)
- node arguments is a raw list and accepts substitutions
- Contributors: Olivier Kermorgant
1.0.5 (2021-09-22)
- automagically convert to expected type for node parameters, remappings, launch arguments
- Contributors: Olivier Kermorgant
1.0.4 (2021-09-03)
- some Python2 legacy bugs
- Contributors: Olivier Kermorgant
1.0.3 (2021-04-17)
- solve typo in node_args
- better handling of node arguments in nested lists
- bug fixes around Substitutions
- Merge pull request #1 from oKermorgant/master deduce executable from package name if needed
- Contributors: Olivier Kermorgant
1.0.2 (2020-12-08)
- composition with existing container
- Contributors: Olivier Kermorgant
1.0.1 (2020-10-12)
- PythonExpression shortcut
- xacro args now take substitution args
- add LoadComposableNode feature for existing containers
- add name_join and path_join to combine raw str and Substitution stuff
- first commit
- Contributors: Olivier Kermorgant
Wiki Tutorials
Package Dependencies
System Dependencies
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Services
Plugins
Recent questions tagged simple_launch at Robotics Stack Exchange
simple_launch package from simple_launch reposimple_launch |
|
Package Summary
Tags | No category tags. |
Version | 1.10.1 |
License | MIT |
Build type | AMENT_CMAKE |
Use | RECOMMENDED |
Repository Summary
Checkout URI | https://github.com/oKermorgant/simple_launch.git |
VCS Type | git |
VCS Version | devel |
Last Updated | 2024-11-21 |
Dev Status | MAINTAINED |
CI status | No Continuous Integration |
Released | RELEASED |
Tags | No category tags. |
Contributing |
Help Wanted (0)
Good First Issues (0) Pull Requests to Review (0) |
Package Description
Additional Links
Maintainers
- Olivier Kermorgant
Authors
simple_launch
This package provides a Python class to help writing ROS 2 launch files.
The motivation behind this package is that the ROS 2 launch Python syntax may not be suited for many simple cases such as running basic nodes, spawning a robot_state_publisher
, and grouping nodes in namespaces or components.
Thanks: this package is inspired by ros2_launch_util.
The entry point is the SimpleLauncher
class, which has several capabilities.
Basic syntax
Namespace and argument parser initialization
sl = SimpleLauncher(namespace = '', use_sim_time = None, scope_included_files = False)
- will initialize all nodes relative to the given namespace
- if
use_sim_time
is a Boolean, creates ause_sim_time
launch argument with this value as the default and forwards it to all nodes, unless explicitely specified when running the node - if
use_sim_time
is'auto'
, thenSimpleLauncher
will set it toTrue
if the/clock
topic is advertized (case of an already running simulation). This may have side effects if the/clock
topic is advertized but you want to use this launch file with system clock. - if
use_sim_time
isNone
(default) then no particular value is forwarded to the nodes - if
scope_included_files
isFalse
(default) then including another launch file that shares the same argument but while passing another value for this argument, will also modify the value of this argument after the inclusion. This is the default behavior oflaunch
but can be undesired. Inside anOpaqueFunction
the behavior is to be scoped anyway (the argument value is resolved) andscope_included_files
has no effect.
Node registration
sl.node(package, executable, **node_args)
where
-
package
is the node package -
executable
is the name of the executable -
node_args
are any additionalNode
arguments
Launch file include
sl.include(package, launch_file, launch_dir = None, launch_arguments=None)
where
-
package
is the package of the included launch file -
launch_file
is the name of the launch file -
launch_dir
is its directory inside the package share (None
to have it found) -
launch_arguments
is a dictionary of arguments to pass to the included launch file
Call a service at launch
This line runs a temporary client that waits for a service and calls it when available:
sl.call_service(server, request = None, verbosity = '')
where
-
server
is the path to some service (possibly namespaced). The service type is deduced when it becomes available. -
request
is a dictionary representing the service request. IfNone
or incomplete, will use the service request default values. -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
If any request parameter is __ns
it will be changed to the current namespace.
Setting parameters
This line runs a temporary client that waits for a node and changes its parameters when available:
sl.set_parameters(node_name, parameters: dict = {}, verbosity = '')
where
-
node_name
is the name of the node (possibly namespaced) -
parameters
is a dictionary of (name, value) parameters to be set -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
This calls the set_parameters
service of the node with the passed types. Possible errors may happen if the parameters do not exist or are of a different type.
Robust types for parameters
In the launch API, differents types are expected for:
- node parameters: a list of dictionaries
- node remappings: a list of (
key
,value
) pairs - included launch arguments: a list of (
key
,value
) pairs - xacro arguments: a concatenation of
key:=value
strings
The sl.include
, sl.node
and xacro_args
calls allow using any type (the simplest being a single dictionary) and will convert to the one expected by the API.
Launch arguments
simple_launch
allows declaring launch arguments and getting them in return.
Declare a launch argument
sl.declare_arg(name, default_value, description = None)
: declare and returns the argument
Contrary to the base API, the default value is a raw Python type.
Retrieve a launch argument
sl.arg(name)
: returns the argument name
as a SimpleSubstitution
Retrieve several arguments as a dictionary
sl.arg_map('robot', 'x', 'y')
: returns {'robot': <robot arg value>, 'x': <x arg value>, 'y': <y arg value>}
Typical when forwarding some launch arguments to a node or an included launch file.
Groups or scopes
Groups are created through the with sl.group():
syntax and accept, a namespace an if/unless condition and an event.
Actions that are added in a scope inherit from all previous defined groups.
By namespace
with sl.group(ns=sub_namespace):
sl.node(package, executable)
From a condition
with sl.group(if_condition=True):
sl.node(package, executable)
with sl.group(unless_condition=<some expression>):
sl.node(package, executable)
- Only one condition can be set in a group, nested condition must be combined first, or used in nested groups.
- Combining conditions coming from launch arguments can be done with
sl.py_eval
as shown below.
From conditional arguments
with sl.group(if_arg='use_gui'):
sl.node(package, executable)
with sl.group(unless_arg='dont_do'):
sl.node(package, executable)
if_arg
/ unless_arg
is expected to be the name of a launch argument. These two lines are equivalent:
with sl.group(if_arg='use_gui'):
with sl.group(if_condition=sl.arg('use_gui')):
If if_arg
/ unless_arg
is not a string then it is considered as a if_condition
/ unless_condition
.
From events
The when
argument wraps events from the launch.event_handlers
module. It combines an event and a delay (0 by default)
from simple_launch.events import When, OnProcessStart, OnProcessExit, OnProcessIO
my_node = sl.node(...) # reference node
with sl.group(when = When(my_node, OnProcessStart, 1.)):
sl.node(...) # will run 1 s after main node starts
with sl.group(when = When(my_node, OnProcessExit)):
sl.node(...) # will run as soon as the main node exists
with sl.group(when = When(my_node, OnProcessIO, io = 'stdout'):
# OnProcessIO events need a function changing the event into an action
sl.add_action(lambda event: LogInfo(msg = 'Node says "{}"'.format(
event.text.decode().strip())))
# several functions can be used if needed, they will be combined in a single one
sl.add_action(lambda event: LogInfo(msg = 'Once again, node says "{}"'.format(
event.text.decode().strip())))
with sl.group(when = When(delay = 2.)):
sl.node(...) # will run after 2 sec
Creating containers
This syntax adds the composition/composition::Talker
as a ComposableNode
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
Use the executable
and package
parameters if you want to use executors other than rclcpp_components
’s component_container
:
with sl.container(name='my_container', output='screen', executable='component_container_isolated'):
It is currently impossible to have group blocks within a container block, as containers can only accept ComposableNode
s. A GroupAction
containing e.g. PushRosNamespace
and a ComposableNode
is not itself a ComposableNode
.
use_sim_time
The current use_sim_time
setting can be retrieved through sl.sim_time
that may be:
-
None
, ifuse_sim_time
was not set in theSimpleLauncher
constructor - a raw Boolean, if
use_sim_time
was set to'auto'
, depending on the/clock
topic being advertized - a Boolean launch argument, if
use_sim_time
was set toTrue
orFalse
In all cases, if the use_sim_time
parameter is explicitely given to a node, it will be used instead of the SimpleLauncher
instance one.
OpaqueFunction
with implicit .perform(context)
Most of the use cases can be dealt with substitutions and with sl.group
blocks.
In order to design more imperative launch files, the OpaqueFunction
approach can be used. The main drawback is that potential errors are harder to track.
To do this with simple_launch
:
- the
SimpleLauncher
instance and the argument declaration should be done in the main body of your launch file. - then, define a function (e.g.
launch_setup
) that takes no argument, where the logic of the launch file resides. - all arguments obtained through
sl.arg
will be basic Python types, obtained from performing the substitutions. - finally just export
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
.
Compare example_launch.py
and example_opaque_launch.py
to see the two approaches on the same logic.
Note that inside an OpaqueFunction
the if/unless idiom reduces to a basic if/else:
# with substitutions
with sl.group(if_arg='some_condition'):
# do stuff
with sl.group(unless_arg='some_condition'):
# do other stuff
# with opaque function
if sl.arg('some_condition'):
# do stuff
else:
# do other stuff
Other one-liners
Methods listed below return instances of SimpleSubstitution
that represent any Substitution, but that provides concatenation (+
) and path concatenation (/
) operators. It is still a Substitution
, not a raw Python type. If run from an OpaqueFunction
the underlying Python variable is returned.
String / substitution concatenation
The following syntax builds the SimpleSubstitution
corresponding to <robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
deprecated: sl.name_join(sl.arg('robot'), '.xacro')
Path concatenation
The following syntax builds the SimpleSubstitution
corresponding to <package_path>/urdf/<robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
urdf_file = os.path.join(get_package_share_directory(package),'urdf')/file_name
Obviously if all the path elements are raw strings, you should use os.path.join
all along.
deprecated: sl.path_join(get_package_share_directory(package), sl.arg('robot'), '.xacro')
Find a share file
path = sl.find(package, file_name = None, file_dir = None)
where:
-
package
is the name of the package orNone
iffile_name
is already an absolute path -
file_name
is the name of the file to find -
file_dir
is the path inside the package
If file_dir
is None
but package
and file_name
are raw strings then the find
function will actually look for the file inside the package share, using os.walk
.
If file_name
is None
then the function just returns the path to the package share directory (e.g. get_package_share_directory(package)
)
Robot state publisher
It is quite common to run a robot_state_publisher
from a urdf
or xacro
file. The line below runs it at the current namespace / condition level:
sl.robot_state_publisher(package, description_file, description_dir=None, xacro_args=None, **node_args)
where
-
description_file
is a URDF or xacro file -
description_dir
is the sub-directory of the file. If omitted, let the script search for the file assuming it is a raw string -
xacro_args
is a dictionary of arguments to forward to xacro -
node_args
are any additional arguments forrobot_state_publisher
(remappings / parameters)
Python expressions
sl.py_eval
will evaluate the given arguments as a Python expression, possibly performed if in an Opaque Function.
# RGB color as a list of [0-255] integers
sl.declare_arg('color', [255,0,0])
# same color as a string of [0-1] numbers (URDF format), note the padding commas to get a string
xacro_color = "'" + sl.py_eval("' '.join(str(c/255) for c in ", sl.arg('color'), ')') + "'"
Conditions
sl.py_eval
can be used to combine conditions. It is robust to lower case true
or false
and will return a SimpleSubstitution
.
sl.declare_arg('some_condition', True)
opposed = sl.py_eval('not ', sl.arg('some_condition'))
Note that IfCondition
and UnlessCondition
cannot be combined, only the underlying Substitution
s can.
Joint state publisher
sl.joint_state_publisher(use_gui, **node_args)
: fires up a joint_state_publisher
, with or without the gui, in the current namespace.
Rviz
sl.rviz(config_file = None, warnings = False)
: runs RViz on the given configuration file. If warnings
is False
(default) then runs with log-level FATAL
in order to avoid many messages in the console.
Classical use case: sl.rviz(sl.find('my_package', 'some_rviz_config.rviz'))
Fallback to low-level syntax
If any unavailable functionality is needed, the sl.add_action(action)
function adds any passed Action
at the current namespace / conditional / event level.
Interaction with Gazebo / Ignition
Note: Ignition being renamed to Gazebo, all tools in this section use Gazebo / gz names
An effort was made to be robust to Ignition versus Gazebo uses, i.e. ign prefix is used for foxy
and galactic
while gz prefix is used from humble
. GZ_VERSION
and IGNITION_VERSION
environment variables are also used to identify which version should be preferred.
Launch Gazebo
The Gazebo launch file corresponding to the current ROS 2 distribution is launched with
sl.gz_launch(world_file, gz_arguments)
Namely, it will redirect to either ros_ign_gazebo/ign_gazebo.launch.py
(foxy
, galactic
) or ros_gz_sim/gz_sim.launch.py
(humble
+).
The given gz_arguments
, if any, will be forwarded either as the ign_args
or gz_args
, accordingly.
If the world file can be parsed then SimpleLaunch
will detect its name and forward it to GazeboBridge
functions.
Spawn a model
The following function allows easily spawing a model from its robot_description
:
sl.spawn_gz_model(name, topic, model_file = None, spawn_args = [], only_new = True)
-
name
is the name this model will get in Gazebo -
topic
is the topic to obtain the model from, default isrobot_description
(relative to the current namespace) -
model_file
is the path to the (urdf or sdf) file. If defined then this will spawn this model and ignore the topic -
only_new
if True, will not spawn the model if it already exists in a running Gazebo instance -
spawn_args
are any additional spawn arguments, e.g. the initial pose
example: sl.spawn_gz_model('my_robot', model_file = sl.find('my_pkg', 'my_model.urdf'))
Declare initial pose
Calling sl.declare_gazebo_axes()
will declare all 6 parameters (x,y,z,roll,pitch,yaw)
with 0
as default values.
If any axis is given (e.g. sl.declare_gazebo_axes(yaw = 3.14)
then only this parameter will be declared.
Such parameters can be retrieved through sl.gazebo_axes_args()
. As a consequence, it is easy to spawn a model with:
sl.declare_gazebo_axes()
sl.robot_description(...)
sl.spawn_gz_model(name, spawn_args = sl.gazebo_axes_args())
Save current world
If the simulation is reset after some models have been spawned, they will disappear. A convenient way to avoid this is to generate the full SDF world from a running simulation. The Gazebo GUI is able to export the current world but cannot resolve models that were spawned from e.g. a robot_description
topic.
The script generate_gz_world
will generate a SDF corresponding to the current simulation. If some models have been spawned from URDF and topics, the script will get the corresponding description and insert it into the SDF, assuming robot name
has its description under /name/robot_description
. It can also be called from a launch file with (see Gazebo example):
# you might want to add a delay to be sure all models have been spawned
sl.save_gz_world(full_world.sdf, after = 1.)
Such a self-contained SDF world file is then compatible with a reset of the simulation. See Gazebo example for launch file that checks if the full world is available.
Gazebo bridge
The GazeboBridge
class allows easily creating bridges when using Gazebo.
An instance is created with: bridge = GazeboBridge(<gazebo_topic>, <ros_topic>, <ros_message>, direction, <gz_message> = None)
where direction
is either:
-
GazeboBridge.gz2ros
for Gazebo -> ROS -
GazeboBridge.ros2gz
for ROS -> Gazebo -
GazeboBridge.bidirectional
for both
The Gazebo message type is deduced from the ROS message type if not set. Remapping will be set to the given ros_topic
.
The SimpleLauncher instance can then run a node dealing with declared bridges, as illustrated in the examples at this end of this document.
sl.create_gz_bridge([bridges], <node_name>)
If some bridges involve sensor_msgs/Image
then a dedicated ros_gz_image
bridge will be used. The corresponding camera_info
topic will be also bridged.
Interaction with Gazebo sim
Some bridges (e.g. joint_states
) need to have information on the world name. This name can only be obtained while Gazebo is running, or by having a priori knowledge of the world file.
The GazeboBridge
class has a few static methods to get information on the simulated world, namely:
-
GazeboBridge.world()
returns the current world name -
GazeboBridge.set_world_name(world)
imposes the world name -
GazeboBridge.model_prefix(model)
builds the Gazebo topic relative to the given model/world/<world>/model/<model>
They can be used under these conditions:
-
sl.gz_launch
was called first (in the same launch setup) and the world file could be parsed, in this case the world name from the file is used - or
GazeboBridge.set_world_name(world)
was called first (in the same launch setup), in this case this world name is used - if none of the above and a running Gazebo instance exists, in this case
GazeboBridge
will request information on the world
If none of these conditions hold, the launch file will not be able to get information on the world, and launch fill probably fail.
Built-in bridges
A common instance of the bridge is the clock. This one can be:
- created with
GazeboBridge.clock()
: returns aGazeboBridge
instance, not added to any node yet - or run directly with
sl.create_gz_clock_bridge()
(actually runssl.create_gz_bridge(GazeboBridge.clock())
)
Another common but tedious bridge instance is the joint state topic of a given model. This topic includes, in Gazebo, the name of the world and of the model. Assuming the world name is known, the corresponding bridge can be created with:
GazeboBridge.joint_states_bridge(model)
- actually runs
GazeboBridge('/world/<world>/model/<model>/joint_state', 'joint_states', 'sensor_msgs/JointState', GazeboBridge.gz2ros)
World TF publisher
If /tf
is used with Gazebo, then the root frame used by Gazebo depends on the world name. This frame is usually world
on the ROS side.
A trivial static_transform_publisher
is run to connect these two frames if they have different names:
-
sl.gz_world_tf(world_frame = None)
: run astatic_transform_publisher
fromworld
toworld_frame
. IfNone
then detect the one currently used by Gazebo.
Examples
Examples can be found in the corresponding folder.
Launch with arguments
Here is a file spawning a robot_state_publisher
and its joint_state_publisher
, where:
-
prefix
,x
andy
are launch arguments that are passed to xacro -
use_gui
tells whetherjoint_state_publisher
should run the gui
from simple_launch import SimpleLauncher
def generate_launch_description():
'''
Launch description for a single robot - runs the two nodes in their own namespace
'''
sl = SimpleLauncher()
sl.declare_arg('prefix', default_value = '', description='name of the robot (+ tf prefix)')
sl.declare_arg('x', default_value = 0, description='x-offset of the robot')
sl.declare_arg('y', default_value = 0, description='y-offset of the robot')
sl.declare_arg('use_gui', default_value = True, description='Use JSP gui')
xacro_args = sl.arg_map('prefix', 'x', 'y')
xacro_args['prefix'] += '/' # can sum substitutions and strings
with sl.group(ns=sl.arg('prefix')):
sl.robot_state_publisher('simple_launch', 'turret.xacro', xacro_args = xacro_args)
sl.joint_state_publisher(use_gui = sl.arg('use_gui'))
return sl.launch_description()
Conditional blocks and includes
The file below fires up either robot1
or robot2
(or both) and also has a boolean argument to spawn RViz2
:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
with sl.group(if_arg='robot1'):
sl.include('simple_launch', 'included_launch.py',
launch_arguments = {'prefix': 'robot1'})
with sl.group(if_arg='robot2'):
with sl.group(unless_arg='no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
sl.include('simple_launch', 'included_launch.py', launch_arguments=args)
with sl.group(if_arg='rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
Conditions with OpaqueFunction
The file below does the same as the previous one, but using an OpaqueFunction
:
from simple_launch import SimpleLauncher
# declare simple launcher and the launch arguments in the main body
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
# string args
sl.declare_arg('included', default_value = 'included_launch')
# define the opaque function, context will be wrapped in the SimpleLauncher instance
def launch_setup():
# we can use raw if as `robot1` argument is performed to a Boolean
if sl.arg('robot1'):
sl.include('simple_launch', 'included_launch.py', launch_arguments = {'prefix': 'robot1'})
# and even combine conditions
if sl.arg('robot2') and not sl.arg('no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
# summing up args and strings
sl.include('simple_launch', sl.arg('included') + '.py', launch_arguments=args)
if sl.arg('rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
# tell SimpleLauncher to rely on the opaque_function in the launch description
# /!\ no `def generate_launch_description():`
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
Combining conditions
The file below shows how to use sl.py_eval
to combine conditions. We have to build a valid Python expression, not forgetting the spaces around and
, or
, not
, etc.
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
cond1 = sl.declare_arg('cond1', True)
cond2 = sl.declare_arg('cond2', False)
for logic in ('and', 'or'):
# builds <cond1> <logic> <cond2> Python expression
combined = sl.py_eval(cond1, f' {logic} ', cond2)
sl.log_info([f'{logic} condition is ', combined])
with sl.group(if_condition = combined):
sl.node('demo_nodes_cpp', 'talker', name = f'talker_{logic}')
# also works with sl.node(..., condition = IfCondition(combined))
return sl.launch_description()
Composition
The file below is another way to write the composition launch example:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
sl.node(package='composition', plugin='Listener', name='listener')
return sl.launch_description()
Events and parameters
This example file is another way to write the event launch example. If does a little more work and is a little smarter, as the passed new_background_r
is applied as soon as it has a valid value.
auto sim time
Here we run Gazebo and force all other nodes to use_sim_time:=True
, unless this file is included from another one with use_sim_time:=False
.
This is unlikely as this launch file spawns a simulator.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
# all nodes in this launch file will use_sim_time:=True
sl = SimpleLauncher(use_sim_time=True)
# run Gazebo + clock bridge
sl.gz_launch(<path/to/some/sdf/world>, '-r')
sl.create_gz_clock_bridge()
# run other nodes with sim time
return sl.launch_description()
Robot description and conditionnal Gazebo bridge
The file below only runs by default a robot_state_publisher
with use_sim_time:=False
.
However, if it is included from another file with use_sim_time:=True
then it also spawns the robot into Gazebo and runs two bridges for joint states and pose.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
sl = SimpleLauncher(use_sim_time=False)
# namespace is a launch argument, not a Python string
sl.declare_arg('robot', default_value = 'robot1')
robot = sl.arg('robot')
with sl.group(ns = robot):
# robot_state_publisher is always run
sl.robot_state_publisher('my_description', 'my_robot.xacro')
with sl.group(if_condition = sl.sim_time):
# only execute this group if use_sim_time was set to True
# spawn in Gazebo at default pose if not already here
sl.spawn_gz_model(robot)
# create a bridge for joint states @ /world/<world>/model/<robot>/joint_state
# note the relative ROS topic 'joint_states' that is actually namespaced
gz_js_topic = GazeboBridge.model_prefix(robot)/'joint_state'
js_bridge = GazeboBridge(gz_topic = gz_js_topic,
ros_topic = 'joint_states',
msg = 'sensor_msgs/JointState',
direction = GazeboBridge.gz2ros)
# pose publisher bridge @ /model/<robot>
pose_bridge = GazeboBridge('/model'/robot/'/pose',
'pose_gt', 'geometry_msgs/Pose', GazeboBridge.gz2ros)
# create bridge node with these two topics with default name gz_bridge
sl.create_gz_bridge([js_bridge, pose_bridge])
return sl.launch_description()
Full Gazebo simulation
The file example/gazebo/gazebo_launch.py
runs a basic simulation of a turret robot with a camera, also displayed in RViz.
ros2 launch simple_launch gazebo_launch.py
You can move the robot around with a joint velocity setpoint (std_msgs/Float64
) on /turret/joint#
and see the simulated camera on /turret/image
.
I want more examples
Other self-contained examples (and slides) have been used to teach the ROS 2 launch file system and the nav stack.
Various aspects of the launch systen are shown in the anf_launch package.
A simple tutorial on Nav2
using simple_launch
is available in the anf_nav package.
Changelog for package simple_launch
1.10.1 (2024-07-05)
- check for gz/ign executable being available
- gz_world_tf + better guess on Gz vs Ign
- Contributors: Olivier Kermorgant
1.10.0 (2024-06-16)
- scope_included_files to include other launch files in a Group and avoid changing my scope
- remove dead code about prefixing gz plugins
- forward sim_time even for nodes that load a parameter file
- lazy GazeboBridge
- Contributors: Olivier Kermorgant
1.9.2 (2024-03-25)
- Gazebo basic example: launch SDF world + spawn from xacro
- remove dead code related to Gazebo.
- sl.arg returns a SimpleSubstitution to allow concatenation
- auto-detect Gazebo world name, allows running the simulation + spawn models in the same launch file
- Type debug on String being Iterable
- better handling of non-string choices in argument declaration
- more robust to various gz/ros combinations
- Contributors: Olivier Kermorgant
1.9.1 (2024-02-20)
- simplify + debug logic of SimpleSubstitution divisions
- image instead of /image to be detected as an image topic
- remove auto_sim_time function
- more robust to various combinations of ROS and Gazebo
- default Gazebo is still ignition Fortress, better error message about GZ_VERSION
- add new bridges for Gazebo
- Contributors: Olivier Kermorgant
1.9.0 (2023-11-23)
- update documentation
- warnings/errors on misuse of GazeboBridge
- move example executable to share directory
- dict cannot be updated with | in Foxy, fallback to dict.update
- absolute container name when loading in existing container
- py_eval can now handle conditions
- Contributors: Olivier Kermorgant
1.8.0 (2023-11-20)
- sync documentation and examples
- when instead of after for events
- scoped events
- add event wrapper
- Contributors: Olivier Kermorgant
1.7.2 (2023-10-02)
- simplify logic of try_perform
- Merge pull request #5 from okvik/devel Fix string-valued launch argument substitution
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant, Viktor Pocedulic
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant
1.7.1 (2023-05-16)
- list[] -> List[] for type hints in 20.04
- detail on __ns for services
- add service call at launch
- Contributors: Olivier Kermorgant
1.7.0 (2023-02-22)
- GazeboBridge creates a camera_info topic for all bridged image topics
- Contributors: Olivier Kermorgant
1.6.2 (2023-01-23)
- add .rviz shortcut, clean Python scripts
- Contributors: Olivier Kermorgant
1.6.1 (2022-10-10)
- fix bug in robot_state_publisher with raw URDF
- Contributors: Olivier Kermorgant
1.6.0 (2022-10-06)
- check use_sim_time versus a parameter file
- resolve any builtin type as Substitution, not only text
- improve documentation
- Gazebo + humble compat
- OpaqueFunction wrapper and SimpleSubstitution
- switch to CMake to avoid deprecation messages
- more spawn_gz
- Contributors: Olivier Kermorgant
1.5.0 (2022-08-26)
- allow spawning a Gz model from file
- parameters are list of dict
- allow substitution for topics in ros_ign_image bridge
- Gazebo bridge handles invalid ROS topics through yaml config file. Image bridges are automatically run through ros_ign_image
- better handling of gazebo spawn pose
- Contributors: Olivier Kermorgant
1.4.1 (2022-06-01)
- more handling of param types
- Contributors: Olivier Kermorgant
1.4.0 (2022-06-01)
- use Gazebo instead of Ignition
- better type comprehension
- Contributors: Olivier Kermorgant
1.3.1 (2022-05-02)
- use underscores in setup.cfg
- typo in included_launch example
- Merge pull request #4 from yushijinhun/patch-1 Add package & executable parameter to container
- [readme] add doc for container.package
- Add package & executable param to container This allows the user to use a component container implementation other than [component_container]{.title-ref}, such as [component_container_isolated]{.title-ref} and [component_container_mt]{.title-ref}.
- Contributors: Haowei Wen, Olivier Kermorgant
1.3.0 (2022-02-03)
- more use_sim_time: constructor + warning on 'auto'
- auto_sim_time can be forced instead of checking /clock
- Contributors: Olivier Kermorgant
1.2.1 (2022-01-24)
- add Ignition support
- Contributors: Olivier Kermorgant
1.2.0 (2021-11-02)
- make it clearer for the prefix_gz_plugins param
- Contributors: Olivier Kermorgant
1.1.0 (2021-09-25)
- add capacity to prefix and namespace Gazebo-published messages, as an alternative to using Gazebo namespaces that also remap /tf
- Contributors: Olivier Kermorgant
1.0.6 (2021-09-22)
- node arguments is a raw list and accepts substitutions
- Contributors: Olivier Kermorgant
1.0.5 (2021-09-22)
- automagically convert to expected type for node parameters, remappings, launch arguments
- Contributors: Olivier Kermorgant
1.0.4 (2021-09-03)
- some Python2 legacy bugs
- Contributors: Olivier Kermorgant
1.0.3 (2021-04-17)
- solve typo in node_args
- better handling of node arguments in nested lists
- bug fixes around Substitutions
- Merge pull request #1 from oKermorgant/master deduce executable from package name if needed
- Contributors: Olivier Kermorgant
1.0.2 (2020-12-08)
- composition with existing container
- Contributors: Olivier Kermorgant
1.0.1 (2020-10-12)
- PythonExpression shortcut
- xacro args now take substitution args
- add LoadComposableNode feature for existing containers
- add name_join and path_join to combine raw str and Substitution stuff
- first commit
- Contributors: Olivier Kermorgant
Wiki Tutorials
Package Dependencies
System Dependencies
Dependant Packages
Launch files
Messages
Services
Plugins
Recent questions tagged simple_launch at Robotics Stack Exchange
simple_launch package from simple_launch reposimple_launch |
|
Package Summary
Tags | No category tags. |
Version | 1.10.1 |
License | MIT |
Build type | AMENT_CMAKE |
Use | RECOMMENDED |
Repository Summary
Checkout URI | https://github.com/oKermorgant/simple_launch.git |
VCS Type | git |
VCS Version | devel |
Last Updated | 2024-11-21 |
Dev Status | MAINTAINED |
CI status | No Continuous Integration |
Released | RELEASED |
Tags | No category tags. |
Contributing |
Help Wanted (0)
Good First Issues (0) Pull Requests to Review (0) |
Package Description
Additional Links
Maintainers
- Olivier Kermorgant
Authors
simple_launch
This package provides a Python class to help writing ROS 2 launch files.
The motivation behind this package is that the ROS 2 launch Python syntax may not be suited for many simple cases such as running basic nodes, spawning a robot_state_publisher
, and grouping nodes in namespaces or components.
Thanks: this package is inspired by ros2_launch_util.
The entry point is the SimpleLauncher
class, which has several capabilities.
Basic syntax
Namespace and argument parser initialization
sl = SimpleLauncher(namespace = '', use_sim_time = None, scope_included_files = False)
- will initialize all nodes relative to the given namespace
- if
use_sim_time
is a Boolean, creates ause_sim_time
launch argument with this value as the default and forwards it to all nodes, unless explicitely specified when running the node - if
use_sim_time
is'auto'
, thenSimpleLauncher
will set it toTrue
if the/clock
topic is advertized (case of an already running simulation). This may have side effects if the/clock
topic is advertized but you want to use this launch file with system clock. - if
use_sim_time
isNone
(default) then no particular value is forwarded to the nodes - if
scope_included_files
isFalse
(default) then including another launch file that shares the same argument but while passing another value for this argument, will also modify the value of this argument after the inclusion. This is the default behavior oflaunch
but can be undesired. Inside anOpaqueFunction
the behavior is to be scoped anyway (the argument value is resolved) andscope_included_files
has no effect.
Node registration
sl.node(package, executable, **node_args)
where
-
package
is the node package -
executable
is the name of the executable -
node_args
are any additionalNode
arguments
Launch file include
sl.include(package, launch_file, launch_dir = None, launch_arguments=None)
where
-
package
is the package of the included launch file -
launch_file
is the name of the launch file -
launch_dir
is its directory inside the package share (None
to have it found) -
launch_arguments
is a dictionary of arguments to pass to the included launch file
Call a service at launch
This line runs a temporary client that waits for a service and calls it when available:
sl.call_service(server, request = None, verbosity = '')
where
-
server
is the path to some service (possibly namespaced). The service type is deduced when it becomes available. -
request
is a dictionary representing the service request. IfNone
or incomplete, will use the service request default values. -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
If any request parameter is __ns
it will be changed to the current namespace.
Setting parameters
This line runs a temporary client that waits for a node and changes its parameters when available:
sl.set_parameters(node_name, parameters: dict = {}, verbosity = '')
where
-
node_name
is the name of the node (possibly namespaced) -
parameters
is a dictionary of (name, value) parameters to be set -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
This calls the set_parameters
service of the node with the passed types. Possible errors may happen if the parameters do not exist or are of a different type.
Robust types for parameters
In the launch API, differents types are expected for:
- node parameters: a list of dictionaries
- node remappings: a list of (
key
,value
) pairs - included launch arguments: a list of (
key
,value
) pairs - xacro arguments: a concatenation of
key:=value
strings
The sl.include
, sl.node
and xacro_args
calls allow using any type (the simplest being a single dictionary) and will convert to the one expected by the API.
Launch arguments
simple_launch
allows declaring launch arguments and getting them in return.
Declare a launch argument
sl.declare_arg(name, default_value, description = None)
: declare and returns the argument
Contrary to the base API, the default value is a raw Python type.
Retrieve a launch argument
sl.arg(name)
: returns the argument name
as a SimpleSubstitution
Retrieve several arguments as a dictionary
sl.arg_map('robot', 'x', 'y')
: returns {'robot': <robot arg value>, 'x': <x arg value>, 'y': <y arg value>}
Typical when forwarding some launch arguments to a node or an included launch file.
Groups or scopes
Groups are created through the with sl.group():
syntax and accept, a namespace an if/unless condition and an event.
Actions that are added in a scope inherit from all previous defined groups.
By namespace
with sl.group(ns=sub_namespace):
sl.node(package, executable)
From a condition
with sl.group(if_condition=True):
sl.node(package, executable)
with sl.group(unless_condition=<some expression>):
sl.node(package, executable)
- Only one condition can be set in a group, nested condition must be combined first, or used in nested groups.
- Combining conditions coming from launch arguments can be done with
sl.py_eval
as shown below.
From conditional arguments
with sl.group(if_arg='use_gui'):
sl.node(package, executable)
with sl.group(unless_arg='dont_do'):
sl.node(package, executable)
if_arg
/ unless_arg
is expected to be the name of a launch argument. These two lines are equivalent:
with sl.group(if_arg='use_gui'):
with sl.group(if_condition=sl.arg('use_gui')):
If if_arg
/ unless_arg
is not a string then it is considered as a if_condition
/ unless_condition
.
From events
The when
argument wraps events from the launch.event_handlers
module. It combines an event and a delay (0 by default)
from simple_launch.events import When, OnProcessStart, OnProcessExit, OnProcessIO
my_node = sl.node(...) # reference node
with sl.group(when = When(my_node, OnProcessStart, 1.)):
sl.node(...) # will run 1 s after main node starts
with sl.group(when = When(my_node, OnProcessExit)):
sl.node(...) # will run as soon as the main node exists
with sl.group(when = When(my_node, OnProcessIO, io = 'stdout'):
# OnProcessIO events need a function changing the event into an action
sl.add_action(lambda event: LogInfo(msg = 'Node says "{}"'.format(
event.text.decode().strip())))
# several functions can be used if needed, they will be combined in a single one
sl.add_action(lambda event: LogInfo(msg = 'Once again, node says "{}"'.format(
event.text.decode().strip())))
with sl.group(when = When(delay = 2.)):
sl.node(...) # will run after 2 sec
Creating containers
This syntax adds the composition/composition::Talker
as a ComposableNode
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
Use the executable
and package
parameters if you want to use executors other than rclcpp_components
’s component_container
:
with sl.container(name='my_container', output='screen', executable='component_container_isolated'):
It is currently impossible to have group blocks within a container block, as containers can only accept ComposableNode
s. A GroupAction
containing e.g. PushRosNamespace
and a ComposableNode
is not itself a ComposableNode
.
use_sim_time
The current use_sim_time
setting can be retrieved through sl.sim_time
that may be:
-
None
, ifuse_sim_time
was not set in theSimpleLauncher
constructor - a raw Boolean, if
use_sim_time
was set to'auto'
, depending on the/clock
topic being advertized - a Boolean launch argument, if
use_sim_time
was set toTrue
orFalse
In all cases, if the use_sim_time
parameter is explicitely given to a node, it will be used instead of the SimpleLauncher
instance one.
OpaqueFunction
with implicit .perform(context)
Most of the use cases can be dealt with substitutions and with sl.group
blocks.
In order to design more imperative launch files, the OpaqueFunction
approach can be used. The main drawback is that potential errors are harder to track.
To do this with simple_launch
:
- the
SimpleLauncher
instance and the argument declaration should be done in the main body of your launch file. - then, define a function (e.g.
launch_setup
) that takes no argument, where the logic of the launch file resides. - all arguments obtained through
sl.arg
will be basic Python types, obtained from performing the substitutions. - finally just export
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
.
Compare example_launch.py
and example_opaque_launch.py
to see the two approaches on the same logic.
Note that inside an OpaqueFunction
the if/unless idiom reduces to a basic if/else:
# with substitutions
with sl.group(if_arg='some_condition'):
# do stuff
with sl.group(unless_arg='some_condition'):
# do other stuff
# with opaque function
if sl.arg('some_condition'):
# do stuff
else:
# do other stuff
Other one-liners
Methods listed below return instances of SimpleSubstitution
that represent any Substitution, but that provides concatenation (+
) and path concatenation (/
) operators. It is still a Substitution
, not a raw Python type. If run from an OpaqueFunction
the underlying Python variable is returned.
String / substitution concatenation
The following syntax builds the SimpleSubstitution
corresponding to <robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
deprecated: sl.name_join(sl.arg('robot'), '.xacro')
Path concatenation
The following syntax builds the SimpleSubstitution
corresponding to <package_path>/urdf/<robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
urdf_file = os.path.join(get_package_share_directory(package),'urdf')/file_name
Obviously if all the path elements are raw strings, you should use os.path.join
all along.
deprecated: sl.path_join(get_package_share_directory(package), sl.arg('robot'), '.xacro')
Find a share file
path = sl.find(package, file_name = None, file_dir = None)
where:
-
package
is the name of the package orNone
iffile_name
is already an absolute path -
file_name
is the name of the file to find -
file_dir
is the path inside the package
If file_dir
is None
but package
and file_name
are raw strings then the find
function will actually look for the file inside the package share, using os.walk
.
If file_name
is None
then the function just returns the path to the package share directory (e.g. get_package_share_directory(package)
)
Robot state publisher
It is quite common to run a robot_state_publisher
from a urdf
or xacro
file. The line below runs it at the current namespace / condition level:
sl.robot_state_publisher(package, description_file, description_dir=None, xacro_args=None, **node_args)
where
-
description_file
is a URDF or xacro file -
description_dir
is the sub-directory of the file. If omitted, let the script search for the file assuming it is a raw string -
xacro_args
is a dictionary of arguments to forward to xacro -
node_args
are any additional arguments forrobot_state_publisher
(remappings / parameters)
Python expressions
sl.py_eval
will evaluate the given arguments as a Python expression, possibly performed if in an Opaque Function.
# RGB color as a list of [0-255] integers
sl.declare_arg('color', [255,0,0])
# same color as a string of [0-1] numbers (URDF format), note the padding commas to get a string
xacro_color = "'" + sl.py_eval("' '.join(str(c/255) for c in ", sl.arg('color'), ')') + "'"
Conditions
sl.py_eval
can be used to combine conditions. It is robust to lower case true
or false
and will return a SimpleSubstitution
.
sl.declare_arg('some_condition', True)
opposed = sl.py_eval('not ', sl.arg('some_condition'))
Note that IfCondition
and UnlessCondition
cannot be combined, only the underlying Substitution
s can.
Joint state publisher
sl.joint_state_publisher(use_gui, **node_args)
: fires up a joint_state_publisher
, with or without the gui, in the current namespace.
Rviz
sl.rviz(config_file = None, warnings = False)
: runs RViz on the given configuration file. If warnings
is False
(default) then runs with log-level FATAL
in order to avoid many messages in the console.
Classical use case: sl.rviz(sl.find('my_package', 'some_rviz_config.rviz'))
Fallback to low-level syntax
If any unavailable functionality is needed, the sl.add_action(action)
function adds any passed Action
at the current namespace / conditional / event level.
Interaction with Gazebo / Ignition
Note: Ignition being renamed to Gazebo, all tools in this section use Gazebo / gz names
An effort was made to be robust to Ignition versus Gazebo uses, i.e. ign prefix is used for foxy
and galactic
while gz prefix is used from humble
. GZ_VERSION
and IGNITION_VERSION
environment variables are also used to identify which version should be preferred.
Launch Gazebo
The Gazebo launch file corresponding to the current ROS 2 distribution is launched with
sl.gz_launch(world_file, gz_arguments)
Namely, it will redirect to either ros_ign_gazebo/ign_gazebo.launch.py
(foxy
, galactic
) or ros_gz_sim/gz_sim.launch.py
(humble
+).
The given gz_arguments
, if any, will be forwarded either as the ign_args
or gz_args
, accordingly.
If the world file can be parsed then SimpleLaunch
will detect its name and forward it to GazeboBridge
functions.
Spawn a model
The following function allows easily spawing a model from its robot_description
:
sl.spawn_gz_model(name, topic, model_file = None, spawn_args = [], only_new = True)
-
name
is the name this model will get in Gazebo -
topic
is the topic to obtain the model from, default isrobot_description
(relative to the current namespace) -
model_file
is the path to the (urdf or sdf) file. If defined then this will spawn this model and ignore the topic -
only_new
if True, will not spawn the model if it already exists in a running Gazebo instance -
spawn_args
are any additional spawn arguments, e.g. the initial pose
example: sl.spawn_gz_model('my_robot', model_file = sl.find('my_pkg', 'my_model.urdf'))
Declare initial pose
Calling sl.declare_gazebo_axes()
will declare all 6 parameters (x,y,z,roll,pitch,yaw)
with 0
as default values.
If any axis is given (e.g. sl.declare_gazebo_axes(yaw = 3.14)
then only this parameter will be declared.
Such parameters can be retrieved through sl.gazebo_axes_args()
. As a consequence, it is easy to spawn a model with:
sl.declare_gazebo_axes()
sl.robot_description(...)
sl.spawn_gz_model(name, spawn_args = sl.gazebo_axes_args())
Save current world
If the simulation is reset after some models have been spawned, they will disappear. A convenient way to avoid this is to generate the full SDF world from a running simulation. The Gazebo GUI is able to export the current world but cannot resolve models that were spawned from e.g. a robot_description
topic.
The script generate_gz_world
will generate a SDF corresponding to the current simulation. If some models have been spawned from URDF and topics, the script will get the corresponding description and insert it into the SDF, assuming robot name
has its description under /name/robot_description
. It can also be called from a launch file with (see Gazebo example):
# you might want to add a delay to be sure all models have been spawned
sl.save_gz_world(full_world.sdf, after = 1.)
Such a self-contained SDF world file is then compatible with a reset of the simulation. See Gazebo example for launch file that checks if the full world is available.
Gazebo bridge
The GazeboBridge
class allows easily creating bridges when using Gazebo.
An instance is created with: bridge = GazeboBridge(<gazebo_topic>, <ros_topic>, <ros_message>, direction, <gz_message> = None)
where direction
is either:
-
GazeboBridge.gz2ros
for Gazebo -> ROS -
GazeboBridge.ros2gz
for ROS -> Gazebo -
GazeboBridge.bidirectional
for both
The Gazebo message type is deduced from the ROS message type if not set. Remapping will be set to the given ros_topic
.
The SimpleLauncher instance can then run a node dealing with declared bridges, as illustrated in the examples at this end of this document.
sl.create_gz_bridge([bridges], <node_name>)
If some bridges involve sensor_msgs/Image
then a dedicated ros_gz_image
bridge will be used. The corresponding camera_info
topic will be also bridged.
Interaction with Gazebo sim
Some bridges (e.g. joint_states
) need to have information on the world name. This name can only be obtained while Gazebo is running, or by having a priori knowledge of the world file.
The GazeboBridge
class has a few static methods to get information on the simulated world, namely:
-
GazeboBridge.world()
returns the current world name -
GazeboBridge.set_world_name(world)
imposes the world name -
GazeboBridge.model_prefix(model)
builds the Gazebo topic relative to the given model/world/<world>/model/<model>
They can be used under these conditions:
-
sl.gz_launch
was called first (in the same launch setup) and the world file could be parsed, in this case the world name from the file is used - or
GazeboBridge.set_world_name(world)
was called first (in the same launch setup), in this case this world name is used - if none of the above and a running Gazebo instance exists, in this case
GazeboBridge
will request information on the world
If none of these conditions hold, the launch file will not be able to get information on the world, and launch fill probably fail.
Built-in bridges
A common instance of the bridge is the clock. This one can be:
- created with
GazeboBridge.clock()
: returns aGazeboBridge
instance, not added to any node yet - or run directly with
sl.create_gz_clock_bridge()
(actually runssl.create_gz_bridge(GazeboBridge.clock())
)
Another common but tedious bridge instance is the joint state topic of a given model. This topic includes, in Gazebo, the name of the world and of the model. Assuming the world name is known, the corresponding bridge can be created with:
GazeboBridge.joint_states_bridge(model)
- actually runs
GazeboBridge('/world/<world>/model/<model>/joint_state', 'joint_states', 'sensor_msgs/JointState', GazeboBridge.gz2ros)
World TF publisher
If /tf
is used with Gazebo, then the root frame used by Gazebo depends on the world name. This frame is usually world
on the ROS side.
A trivial static_transform_publisher
is run to connect these two frames if they have different names:
-
sl.gz_world_tf(world_frame = None)
: run astatic_transform_publisher
fromworld
toworld_frame
. IfNone
then detect the one currently used by Gazebo.
Examples
Examples can be found in the corresponding folder.
Launch with arguments
Here is a file spawning a robot_state_publisher
and its joint_state_publisher
, where:
-
prefix
,x
andy
are launch arguments that are passed to xacro -
use_gui
tells whetherjoint_state_publisher
should run the gui
from simple_launch import SimpleLauncher
def generate_launch_description():
'''
Launch description for a single robot - runs the two nodes in their own namespace
'''
sl = SimpleLauncher()
sl.declare_arg('prefix', default_value = '', description='name of the robot (+ tf prefix)')
sl.declare_arg('x', default_value = 0, description='x-offset of the robot')
sl.declare_arg('y', default_value = 0, description='y-offset of the robot')
sl.declare_arg('use_gui', default_value = True, description='Use JSP gui')
xacro_args = sl.arg_map('prefix', 'x', 'y')
xacro_args['prefix'] += '/' # can sum substitutions and strings
with sl.group(ns=sl.arg('prefix')):
sl.robot_state_publisher('simple_launch', 'turret.xacro', xacro_args = xacro_args)
sl.joint_state_publisher(use_gui = sl.arg('use_gui'))
return sl.launch_description()
Conditional blocks and includes
The file below fires up either robot1
or robot2
(or both) and also has a boolean argument to spawn RViz2
:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
with sl.group(if_arg='robot1'):
sl.include('simple_launch', 'included_launch.py',
launch_arguments = {'prefix': 'robot1'})
with sl.group(if_arg='robot2'):
with sl.group(unless_arg='no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
sl.include('simple_launch', 'included_launch.py', launch_arguments=args)
with sl.group(if_arg='rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
Conditions with OpaqueFunction
The file below does the same as the previous one, but using an OpaqueFunction
:
from simple_launch import SimpleLauncher
# declare simple launcher and the launch arguments in the main body
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
# string args
sl.declare_arg('included', default_value = 'included_launch')
# define the opaque function, context will be wrapped in the SimpleLauncher instance
def launch_setup():
# we can use raw if as `robot1` argument is performed to a Boolean
if sl.arg('robot1'):
sl.include('simple_launch', 'included_launch.py', launch_arguments = {'prefix': 'robot1'})
# and even combine conditions
if sl.arg('robot2') and not sl.arg('no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
# summing up args and strings
sl.include('simple_launch', sl.arg('included') + '.py', launch_arguments=args)
if sl.arg('rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
# tell SimpleLauncher to rely on the opaque_function in the launch description
# /!\ no `def generate_launch_description():`
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
Combining conditions
The file below shows how to use sl.py_eval
to combine conditions. We have to build a valid Python expression, not forgetting the spaces around and
, or
, not
, etc.
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
cond1 = sl.declare_arg('cond1', True)
cond2 = sl.declare_arg('cond2', False)
for logic in ('and', 'or'):
# builds <cond1> <logic> <cond2> Python expression
combined = sl.py_eval(cond1, f' {logic} ', cond2)
sl.log_info([f'{logic} condition is ', combined])
with sl.group(if_condition = combined):
sl.node('demo_nodes_cpp', 'talker', name = f'talker_{logic}')
# also works with sl.node(..., condition = IfCondition(combined))
return sl.launch_description()
Composition
The file below is another way to write the composition launch example:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
sl.node(package='composition', plugin='Listener', name='listener')
return sl.launch_description()
Events and parameters
This example file is another way to write the event launch example. If does a little more work and is a little smarter, as the passed new_background_r
is applied as soon as it has a valid value.
auto sim time
Here we run Gazebo and force all other nodes to use_sim_time:=True
, unless this file is included from another one with use_sim_time:=False
.
This is unlikely as this launch file spawns a simulator.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
# all nodes in this launch file will use_sim_time:=True
sl = SimpleLauncher(use_sim_time=True)
# run Gazebo + clock bridge
sl.gz_launch(<path/to/some/sdf/world>, '-r')
sl.create_gz_clock_bridge()
# run other nodes with sim time
return sl.launch_description()
Robot description and conditionnal Gazebo bridge
The file below only runs by default a robot_state_publisher
with use_sim_time:=False
.
However, if it is included from another file with use_sim_time:=True
then it also spawns the robot into Gazebo and runs two bridges for joint states and pose.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
sl = SimpleLauncher(use_sim_time=False)
# namespace is a launch argument, not a Python string
sl.declare_arg('robot', default_value = 'robot1')
robot = sl.arg('robot')
with sl.group(ns = robot):
# robot_state_publisher is always run
sl.robot_state_publisher('my_description', 'my_robot.xacro')
with sl.group(if_condition = sl.sim_time):
# only execute this group if use_sim_time was set to True
# spawn in Gazebo at default pose if not already here
sl.spawn_gz_model(robot)
# create a bridge for joint states @ /world/<world>/model/<robot>/joint_state
# note the relative ROS topic 'joint_states' that is actually namespaced
gz_js_topic = GazeboBridge.model_prefix(robot)/'joint_state'
js_bridge = GazeboBridge(gz_topic = gz_js_topic,
ros_topic = 'joint_states',
msg = 'sensor_msgs/JointState',
direction = GazeboBridge.gz2ros)
# pose publisher bridge @ /model/<robot>
pose_bridge = GazeboBridge('/model'/robot/'/pose',
'pose_gt', 'geometry_msgs/Pose', GazeboBridge.gz2ros)
# create bridge node with these two topics with default name gz_bridge
sl.create_gz_bridge([js_bridge, pose_bridge])
return sl.launch_description()
Full Gazebo simulation
The file example/gazebo/gazebo_launch.py
runs a basic simulation of a turret robot with a camera, also displayed in RViz.
ros2 launch simple_launch gazebo_launch.py
You can move the robot around with a joint velocity setpoint (std_msgs/Float64
) on /turret/joint#
and see the simulated camera on /turret/image
.
I want more examples
Other self-contained examples (and slides) have been used to teach the ROS 2 launch file system and the nav stack.
Various aspects of the launch systen are shown in the anf_launch package.
A simple tutorial on Nav2
using simple_launch
is available in the anf_nav package.
Changelog for package simple_launch
1.10.1 (2024-07-05)
- check for gz/ign executable being available
- gz_world_tf + better guess on Gz vs Ign
- Contributors: Olivier Kermorgant
1.10.0 (2024-06-16)
- scope_included_files to include other launch files in a Group and avoid changing my scope
- remove dead code about prefixing gz plugins
- forward sim_time even for nodes that load a parameter file
- lazy GazeboBridge
- Contributors: Olivier Kermorgant
1.9.2 (2024-03-25)
- Gazebo basic example: launch SDF world + spawn from xacro
- remove dead code related to Gazebo.
- sl.arg returns a SimpleSubstitution to allow concatenation
- auto-detect Gazebo world name, allows running the simulation + spawn models in the same launch file
- Type debug on String being Iterable
- better handling of non-string choices in argument declaration
- more robust to various gz/ros combinations
- Contributors: Olivier Kermorgant
1.9.1 (2024-02-20)
- simplify + debug logic of SimpleSubstitution divisions
- image instead of /image to be detected as an image topic
- remove auto_sim_time function
- more robust to various combinations of ROS and Gazebo
- default Gazebo is still ignition Fortress, better error message about GZ_VERSION
- add new bridges for Gazebo
- Contributors: Olivier Kermorgant
1.9.0 (2023-11-23)
- update documentation
- warnings/errors on misuse of GazeboBridge
- move example executable to share directory
- dict cannot be updated with | in Foxy, fallback to dict.update
- absolute container name when loading in existing container
- py_eval can now handle conditions
- Contributors: Olivier Kermorgant
1.8.0 (2023-11-20)
- sync documentation and examples
- when instead of after for events
- scoped events
- add event wrapper
- Contributors: Olivier Kermorgant
1.7.2 (2023-10-02)
- simplify logic of try_perform
- Merge pull request #5 from okvik/devel Fix string-valued launch argument substitution
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant, Viktor Pocedulic
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant
1.7.1 (2023-05-16)
- list[] -> List[] for type hints in 20.04
- detail on __ns for services
- add service call at launch
- Contributors: Olivier Kermorgant
1.7.0 (2023-02-22)
- GazeboBridge creates a camera_info topic for all bridged image topics
- Contributors: Olivier Kermorgant
1.6.2 (2023-01-23)
- add .rviz shortcut, clean Python scripts
- Contributors: Olivier Kermorgant
1.6.1 (2022-10-10)
- fix bug in robot_state_publisher with raw URDF
- Contributors: Olivier Kermorgant
1.6.0 (2022-10-06)
- check use_sim_time versus a parameter file
- resolve any builtin type as Substitution, not only text
- improve documentation
- Gazebo + humble compat
- OpaqueFunction wrapper and SimpleSubstitution
- switch to CMake to avoid deprecation messages
- more spawn_gz
- Contributors: Olivier Kermorgant
1.5.0 (2022-08-26)
- allow spawning a Gz model from file
- parameters are list of dict
- allow substitution for topics in ros_ign_image bridge
- Gazebo bridge handles invalid ROS topics through yaml config file. Image bridges are automatically run through ros_ign_image
- better handling of gazebo spawn pose
- Contributors: Olivier Kermorgant
1.4.1 (2022-06-01)
- more handling of param types
- Contributors: Olivier Kermorgant
1.4.0 (2022-06-01)
- use Gazebo instead of Ignition
- better type comprehension
- Contributors: Olivier Kermorgant
1.3.1 (2022-05-02)
- use underscores in setup.cfg
- typo in included_launch example
- Merge pull request #4 from yushijinhun/patch-1 Add package & executable parameter to container
- [readme] add doc for container.package
- Add package & executable param to container This allows the user to use a component container implementation other than [component_container]{.title-ref}, such as [component_container_isolated]{.title-ref} and [component_container_mt]{.title-ref}.
- Contributors: Haowei Wen, Olivier Kermorgant
1.3.0 (2022-02-03)
- more use_sim_time: constructor + warning on 'auto'
- auto_sim_time can be forced instead of checking /clock
- Contributors: Olivier Kermorgant
1.2.1 (2022-01-24)
- add Ignition support
- Contributors: Olivier Kermorgant
1.2.0 (2021-11-02)
- make it clearer for the prefix_gz_plugins param
- Contributors: Olivier Kermorgant
1.1.0 (2021-09-25)
- add capacity to prefix and namespace Gazebo-published messages, as an alternative to using Gazebo namespaces that also remap /tf
- Contributors: Olivier Kermorgant
1.0.6 (2021-09-22)
- node arguments is a raw list and accepts substitutions
- Contributors: Olivier Kermorgant
1.0.5 (2021-09-22)
- automagically convert to expected type for node parameters, remappings, launch arguments
- Contributors: Olivier Kermorgant
1.0.4 (2021-09-03)
- some Python2 legacy bugs
- Contributors: Olivier Kermorgant
1.0.3 (2021-04-17)
- solve typo in node_args
- better handling of node arguments in nested lists
- bug fixes around Substitutions
- Merge pull request #1 from oKermorgant/master deduce executable from package name if needed
- Contributors: Olivier Kermorgant
1.0.2 (2020-12-08)
- composition with existing container
- Contributors: Olivier Kermorgant
1.0.1 (2020-10-12)
- PythonExpression shortcut
- xacro args now take substitution args
- add LoadComposableNode feature for existing containers
- add name_join and path_join to combine raw str and Substitution stuff
- first commit
- Contributors: Olivier Kermorgant
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simple_launch package from simple_launch reposimple_launch |
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Package Summary
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Version | 1.10.1 |
License | MIT |
Build type | AMENT_CMAKE |
Use | RECOMMENDED |
Repository Summary
Checkout URI | https://github.com/oKermorgant/simple_launch.git |
VCS Type | git |
VCS Version | devel |
Last Updated | 2024-11-21 |
Dev Status | MAINTAINED |
CI status | No Continuous Integration |
Released | RELEASED |
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Package Description
Additional Links
Maintainers
- Olivier Kermorgant
Authors
simple_launch
This package provides a Python class to help writing ROS 2 launch files.
The motivation behind this package is that the ROS 2 launch Python syntax may not be suited for many simple cases such as running basic nodes, spawning a robot_state_publisher
, and grouping nodes in namespaces or components.
Thanks: this package is inspired by ros2_launch_util.
The entry point is the SimpleLauncher
class, which has several capabilities.
Basic syntax
Namespace and argument parser initialization
sl = SimpleLauncher(namespace = '', use_sim_time = None, scope_included_files = False)
- will initialize all nodes relative to the given namespace
- if
use_sim_time
is a Boolean, creates ause_sim_time
launch argument with this value as the default and forwards it to all nodes, unless explicitely specified when running the node - if
use_sim_time
is'auto'
, thenSimpleLauncher
will set it toTrue
if the/clock
topic is advertized (case of an already running simulation). This may have side effects if the/clock
topic is advertized but you want to use this launch file with system clock. - if
use_sim_time
isNone
(default) then no particular value is forwarded to the nodes - if
scope_included_files
isFalse
(default) then including another launch file that shares the same argument but while passing another value for this argument, will also modify the value of this argument after the inclusion. This is the default behavior oflaunch
but can be undesired. Inside anOpaqueFunction
the behavior is to be scoped anyway (the argument value is resolved) andscope_included_files
has no effect.
Node registration
sl.node(package, executable, **node_args)
where
-
package
is the node package -
executable
is the name of the executable -
node_args
are any additionalNode
arguments
Launch file include
sl.include(package, launch_file, launch_dir = None, launch_arguments=None)
where
-
package
is the package of the included launch file -
launch_file
is the name of the launch file -
launch_dir
is its directory inside the package share (None
to have it found) -
launch_arguments
is a dictionary of arguments to pass to the included launch file
Call a service at launch
This line runs a temporary client that waits for a service and calls it when available:
sl.call_service(server, request = None, verbosity = '')
where
-
server
is the path to some service (possibly namespaced). The service type is deduced when it becomes available. -
request
is a dictionary representing the service request. IfNone
or incomplete, will use the service request default values. -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
If any request parameter is __ns
it will be changed to the current namespace.
Setting parameters
This line runs a temporary client that waits for a node and changes its parameters when available:
sl.set_parameters(node_name, parameters: dict = {}, verbosity = '')
where
-
node_name
is the name of the node (possibly namespaced) -
parameters
is a dictionary of (name, value) parameters to be set -
verbosity
let the underlying node describe what it is doing:'req'
for request info,'res'
for response info or both with'reqres'
This calls the set_parameters
service of the node with the passed types. Possible errors may happen if the parameters do not exist or are of a different type.
Robust types for parameters
In the launch API, differents types are expected for:
- node parameters: a list of dictionaries
- node remappings: a list of (
key
,value
) pairs - included launch arguments: a list of (
key
,value
) pairs - xacro arguments: a concatenation of
key:=value
strings
The sl.include
, sl.node
and xacro_args
calls allow using any type (the simplest being a single dictionary) and will convert to the one expected by the API.
Launch arguments
simple_launch
allows declaring launch arguments and getting them in return.
Declare a launch argument
sl.declare_arg(name, default_value, description = None)
: declare and returns the argument
Contrary to the base API, the default value is a raw Python type.
Retrieve a launch argument
sl.arg(name)
: returns the argument name
as a SimpleSubstitution
Retrieve several arguments as a dictionary
sl.arg_map('robot', 'x', 'y')
: returns {'robot': <robot arg value>, 'x': <x arg value>, 'y': <y arg value>}
Typical when forwarding some launch arguments to a node or an included launch file.
Groups or scopes
Groups are created through the with sl.group():
syntax and accept, a namespace an if/unless condition and an event.
Actions that are added in a scope inherit from all previous defined groups.
By namespace
with sl.group(ns=sub_namespace):
sl.node(package, executable)
From a condition
with sl.group(if_condition=True):
sl.node(package, executable)
with sl.group(unless_condition=<some expression>):
sl.node(package, executable)
- Only one condition can be set in a group, nested condition must be combined first, or used in nested groups.
- Combining conditions coming from launch arguments can be done with
sl.py_eval
as shown below.
From conditional arguments
with sl.group(if_arg='use_gui'):
sl.node(package, executable)
with sl.group(unless_arg='dont_do'):
sl.node(package, executable)
if_arg
/ unless_arg
is expected to be the name of a launch argument. These two lines are equivalent:
with sl.group(if_arg='use_gui'):
with sl.group(if_condition=sl.arg('use_gui')):
If if_arg
/ unless_arg
is not a string then it is considered as a if_condition
/ unless_condition
.
From events
The when
argument wraps events from the launch.event_handlers
module. It combines an event and a delay (0 by default)
from simple_launch.events import When, OnProcessStart, OnProcessExit, OnProcessIO
my_node = sl.node(...) # reference node
with sl.group(when = When(my_node, OnProcessStart, 1.)):
sl.node(...) # will run 1 s after main node starts
with sl.group(when = When(my_node, OnProcessExit)):
sl.node(...) # will run as soon as the main node exists
with sl.group(when = When(my_node, OnProcessIO, io = 'stdout'):
# OnProcessIO events need a function changing the event into an action
sl.add_action(lambda event: LogInfo(msg = 'Node says "{}"'.format(
event.text.decode().strip())))
# several functions can be used if needed, they will be combined in a single one
sl.add_action(lambda event: LogInfo(msg = 'Once again, node says "{}"'.format(
event.text.decode().strip())))
with sl.group(when = When(delay = 2.)):
sl.node(...) # will run after 2 sec
Creating containers
This syntax adds the composition/composition::Talker
as a ComposableNode
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
Use the executable
and package
parameters if you want to use executors other than rclcpp_components
’s component_container
:
with sl.container(name='my_container', output='screen', executable='component_container_isolated'):
It is currently impossible to have group blocks within a container block, as containers can only accept ComposableNode
s. A GroupAction
containing e.g. PushRosNamespace
and a ComposableNode
is not itself a ComposableNode
.
use_sim_time
The current use_sim_time
setting can be retrieved through sl.sim_time
that may be:
-
None
, ifuse_sim_time
was not set in theSimpleLauncher
constructor - a raw Boolean, if
use_sim_time
was set to'auto'
, depending on the/clock
topic being advertized - a Boolean launch argument, if
use_sim_time
was set toTrue
orFalse
In all cases, if the use_sim_time
parameter is explicitely given to a node, it will be used instead of the SimpleLauncher
instance one.
OpaqueFunction
with implicit .perform(context)
Most of the use cases can be dealt with substitutions and with sl.group
blocks.
In order to design more imperative launch files, the OpaqueFunction
approach can be used. The main drawback is that potential errors are harder to track.
To do this with simple_launch
:
- the
SimpleLauncher
instance and the argument declaration should be done in the main body of your launch file. - then, define a function (e.g.
launch_setup
) that takes no argument, where the logic of the launch file resides. - all arguments obtained through
sl.arg
will be basic Python types, obtained from performing the substitutions. - finally just export
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
.
Compare example_launch.py
and example_opaque_launch.py
to see the two approaches on the same logic.
Note that inside an OpaqueFunction
the if/unless idiom reduces to a basic if/else:
# with substitutions
with sl.group(if_arg='some_condition'):
# do stuff
with sl.group(unless_arg='some_condition'):
# do other stuff
# with opaque function
if sl.arg('some_condition'):
# do stuff
else:
# do other stuff
Other one-liners
Methods listed below return instances of SimpleSubstitution
that represent any Substitution, but that provides concatenation (+
) and path concatenation (/
) operators. It is still a Substitution
, not a raw Python type. If run from an OpaqueFunction
the underlying Python variable is returned.
String / substitution concatenation
The following syntax builds the SimpleSubstitution
corresponding to <robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
deprecated: sl.name_join(sl.arg('robot'), '.xacro')
Path concatenation
The following syntax builds the SimpleSubstitution
corresponding to <package_path>/urdf/<robot arg>.xacro
:
file_name = sl.arg('robot') + '.xacro'
urdf_file = os.path.join(get_package_share_directory(package),'urdf')/file_name
Obviously if all the path elements are raw strings, you should use os.path.join
all along.
deprecated: sl.path_join(get_package_share_directory(package), sl.arg('robot'), '.xacro')
Find a share file
path = sl.find(package, file_name = None, file_dir = None)
where:
-
package
is the name of the package orNone
iffile_name
is already an absolute path -
file_name
is the name of the file to find -
file_dir
is the path inside the package
If file_dir
is None
but package
and file_name
are raw strings then the find
function will actually look for the file inside the package share, using os.walk
.
If file_name
is None
then the function just returns the path to the package share directory (e.g. get_package_share_directory(package)
)
Robot state publisher
It is quite common to run a robot_state_publisher
from a urdf
or xacro
file. The line below runs it at the current namespace / condition level:
sl.robot_state_publisher(package, description_file, description_dir=None, xacro_args=None, **node_args)
where
-
description_file
is a URDF or xacro file -
description_dir
is the sub-directory of the file. If omitted, let the script search for the file assuming it is a raw string -
xacro_args
is a dictionary of arguments to forward to xacro -
node_args
are any additional arguments forrobot_state_publisher
(remappings / parameters)
Python expressions
sl.py_eval
will evaluate the given arguments as a Python expression, possibly performed if in an Opaque Function.
# RGB color as a list of [0-255] integers
sl.declare_arg('color', [255,0,0])
# same color as a string of [0-1] numbers (URDF format), note the padding commas to get a string
xacro_color = "'" + sl.py_eval("' '.join(str(c/255) for c in ", sl.arg('color'), ')') + "'"
Conditions
sl.py_eval
can be used to combine conditions. It is robust to lower case true
or false
and will return a SimpleSubstitution
.
sl.declare_arg('some_condition', True)
opposed = sl.py_eval('not ', sl.arg('some_condition'))
Note that IfCondition
and UnlessCondition
cannot be combined, only the underlying Substitution
s can.
Joint state publisher
sl.joint_state_publisher(use_gui, **node_args)
: fires up a joint_state_publisher
, with or without the gui, in the current namespace.
Rviz
sl.rviz(config_file = None, warnings = False)
: runs RViz on the given configuration file. If warnings
is False
(default) then runs with log-level FATAL
in order to avoid many messages in the console.
Classical use case: sl.rviz(sl.find('my_package', 'some_rviz_config.rviz'))
Fallback to low-level syntax
If any unavailable functionality is needed, the sl.add_action(action)
function adds any passed Action
at the current namespace / conditional / event level.
Interaction with Gazebo / Ignition
Note: Ignition being renamed to Gazebo, all tools in this section use Gazebo / gz names
An effort was made to be robust to Ignition versus Gazebo uses, i.e. ign prefix is used for foxy
and galactic
while gz prefix is used from humble
. GZ_VERSION
and IGNITION_VERSION
environment variables are also used to identify which version should be preferred.
Launch Gazebo
The Gazebo launch file corresponding to the current ROS 2 distribution is launched with
sl.gz_launch(world_file, gz_arguments)
Namely, it will redirect to either ros_ign_gazebo/ign_gazebo.launch.py
(foxy
, galactic
) or ros_gz_sim/gz_sim.launch.py
(humble
+).
The given gz_arguments
, if any, will be forwarded either as the ign_args
or gz_args
, accordingly.
If the world file can be parsed then SimpleLaunch
will detect its name and forward it to GazeboBridge
functions.
Spawn a model
The following function allows easily spawing a model from its robot_description
:
sl.spawn_gz_model(name, topic, model_file = None, spawn_args = [], only_new = True)
-
name
is the name this model will get in Gazebo -
topic
is the topic to obtain the model from, default isrobot_description
(relative to the current namespace) -
model_file
is the path to the (urdf or sdf) file. If defined then this will spawn this model and ignore the topic -
only_new
if True, will not spawn the model if it already exists in a running Gazebo instance -
spawn_args
are any additional spawn arguments, e.g. the initial pose
example: sl.spawn_gz_model('my_robot', model_file = sl.find('my_pkg', 'my_model.urdf'))
Declare initial pose
Calling sl.declare_gazebo_axes()
will declare all 6 parameters (x,y,z,roll,pitch,yaw)
with 0
as default values.
If any axis is given (e.g. sl.declare_gazebo_axes(yaw = 3.14)
then only this parameter will be declared.
Such parameters can be retrieved through sl.gazebo_axes_args()
. As a consequence, it is easy to spawn a model with:
sl.declare_gazebo_axes()
sl.robot_description(...)
sl.spawn_gz_model(name, spawn_args = sl.gazebo_axes_args())
Save current world
If the simulation is reset after some models have been spawned, they will disappear. A convenient way to avoid this is to generate the full SDF world from a running simulation. The Gazebo GUI is able to export the current world but cannot resolve models that were spawned from e.g. a robot_description
topic.
The script generate_gz_world
will generate a SDF corresponding to the current simulation. If some models have been spawned from URDF and topics, the script will get the corresponding description and insert it into the SDF, assuming robot name
has its description under /name/robot_description
. It can also be called from a launch file with (see Gazebo example):
# you might want to add a delay to be sure all models have been spawned
sl.save_gz_world(full_world.sdf, after = 1.)
Such a self-contained SDF world file is then compatible with a reset of the simulation. See Gazebo example for launch file that checks if the full world is available.
Gazebo bridge
The GazeboBridge
class allows easily creating bridges when using Gazebo.
An instance is created with: bridge = GazeboBridge(<gazebo_topic>, <ros_topic>, <ros_message>, direction, <gz_message> = None)
where direction
is either:
-
GazeboBridge.gz2ros
for Gazebo -> ROS -
GazeboBridge.ros2gz
for ROS -> Gazebo -
GazeboBridge.bidirectional
for both
The Gazebo message type is deduced from the ROS message type if not set. Remapping will be set to the given ros_topic
.
The SimpleLauncher instance can then run a node dealing with declared bridges, as illustrated in the examples at this end of this document.
sl.create_gz_bridge([bridges], <node_name>)
If some bridges involve sensor_msgs/Image
then a dedicated ros_gz_image
bridge will be used. The corresponding camera_info
topic will be also bridged.
Interaction with Gazebo sim
Some bridges (e.g. joint_states
) need to have information on the world name. This name can only be obtained while Gazebo is running, or by having a priori knowledge of the world file.
The GazeboBridge
class has a few static methods to get information on the simulated world, namely:
-
GazeboBridge.world()
returns the current world name -
GazeboBridge.set_world_name(world)
imposes the world name -
GazeboBridge.model_prefix(model)
builds the Gazebo topic relative to the given model/world/<world>/model/<model>
They can be used under these conditions:
-
sl.gz_launch
was called first (in the same launch setup) and the world file could be parsed, in this case the world name from the file is used - or
GazeboBridge.set_world_name(world)
was called first (in the same launch setup), in this case this world name is used - if none of the above and a running Gazebo instance exists, in this case
GazeboBridge
will request information on the world
If none of these conditions hold, the launch file will not be able to get information on the world, and launch fill probably fail.
Built-in bridges
A common instance of the bridge is the clock. This one can be:
- created with
GazeboBridge.clock()
: returns aGazeboBridge
instance, not added to any node yet - or run directly with
sl.create_gz_clock_bridge()
(actually runssl.create_gz_bridge(GazeboBridge.clock())
)
Another common but tedious bridge instance is the joint state topic of a given model. This topic includes, in Gazebo, the name of the world and of the model. Assuming the world name is known, the corresponding bridge can be created with:
GazeboBridge.joint_states_bridge(model)
- actually runs
GazeboBridge('/world/<world>/model/<model>/joint_state', 'joint_states', 'sensor_msgs/JointState', GazeboBridge.gz2ros)
World TF publisher
If /tf
is used with Gazebo, then the root frame used by Gazebo depends on the world name. This frame is usually world
on the ROS side.
A trivial static_transform_publisher
is run to connect these two frames if they have different names:
-
sl.gz_world_tf(world_frame = None)
: run astatic_transform_publisher
fromworld
toworld_frame
. IfNone
then detect the one currently used by Gazebo.
Examples
Examples can be found in the corresponding folder.
Launch with arguments
Here is a file spawning a robot_state_publisher
and its joint_state_publisher
, where:
-
prefix
,x
andy
are launch arguments that are passed to xacro -
use_gui
tells whetherjoint_state_publisher
should run the gui
from simple_launch import SimpleLauncher
def generate_launch_description():
'''
Launch description for a single robot - runs the two nodes in their own namespace
'''
sl = SimpleLauncher()
sl.declare_arg('prefix', default_value = '', description='name of the robot (+ tf prefix)')
sl.declare_arg('x', default_value = 0, description='x-offset of the robot')
sl.declare_arg('y', default_value = 0, description='y-offset of the robot')
sl.declare_arg('use_gui', default_value = True, description='Use JSP gui')
xacro_args = sl.arg_map('prefix', 'x', 'y')
xacro_args['prefix'] += '/' # can sum substitutions and strings
with sl.group(ns=sl.arg('prefix')):
sl.robot_state_publisher('simple_launch', 'turret.xacro', xacro_args = xacro_args)
sl.joint_state_publisher(use_gui = sl.arg('use_gui'))
return sl.launch_description()
Conditional blocks and includes
The file below fires up either robot1
or robot2
(or both) and also has a boolean argument to spawn RViz2
:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
with sl.group(if_arg='robot1'):
sl.include('simple_launch', 'included_launch.py',
launch_arguments = {'prefix': 'robot1'})
with sl.group(if_arg='robot2'):
with sl.group(unless_arg='no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
sl.include('simple_launch', 'included_launch.py', launch_arguments=args)
with sl.group(if_arg='rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
Conditions with OpaqueFunction
The file below does the same as the previous one, but using an OpaqueFunction
:
from simple_launch import SimpleLauncher
# declare simple launcher and the launch arguments in the main body
sl = SimpleLauncher()
# conditional args
sl.declare_arg('robot1', default_value=True, description='use robot 1')
sl.declare_arg('robot2', default_value=True, description='use robot 2')
sl.declare_arg('no_robot2', default_value=False, description='cancel use of robot 2')
sl.declare_arg('rviz', default_value=True, description='Bringup RViz2')
# numeric args
sl.declare_arg('robot2_x', default_value=1, description='x-offset of robot 2')
sl.declare_arg('robot2_y', default_value=1, description='y-offset of robot 2')
# string args
sl.declare_arg('included', default_value = 'included_launch')
# define the opaque function, context will be wrapped in the SimpleLauncher instance
def launch_setup():
# we can use raw if as `robot1` argument is performed to a Boolean
if sl.arg('robot1'):
sl.include('simple_launch', 'included_launch.py', launch_arguments = {'prefix': 'robot1'})
# and even combine conditions
if sl.arg('robot2') and not sl.arg('no_robot2'):
args = {'prefix': 'robot2', 'x':sl.arg('robot2_x'), 'y': sl.arg('robot2_y')}
# summing up args and strings
sl.include('simple_launch', sl.arg('included') + '.py', launch_arguments=args)
if sl.arg('rviz'):
rviz_config = sl.find('simple_launch', 'turret.rviz')
sl.node('rviz2', 'rviz2', arguments = ['-d', rviz_config])
return sl.launch_description()
# tell SimpleLauncher to rely on the opaque_function in the launch description
# /!\ no `def generate_launch_description():`
generate_launch_description = sl.launch_description(opaque_function = launch_setup)
Combining conditions
The file below shows how to use sl.py_eval
to combine conditions. We have to build a valid Python expression, not forgetting the spaces around and
, or
, not
, etc.
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
cond1 = sl.declare_arg('cond1', True)
cond2 = sl.declare_arg('cond2', False)
for logic in ('and', 'or'):
# builds <cond1> <logic> <cond2> Python expression
combined = sl.py_eval(cond1, f' {logic} ', cond2)
sl.log_info([f'{logic} condition is ', combined])
with sl.group(if_condition = combined):
sl.node('demo_nodes_cpp', 'talker', name = f'talker_{logic}')
# also works with sl.node(..., condition = IfCondition(combined))
return sl.launch_description()
Composition
The file below is another way to write the composition launch example:
from simple_launch import SimpleLauncher
def generate_launch_description():
sl = SimpleLauncher()
with sl.container(name='my_container', output='screen'):
sl.node(package='composition', plugin='Talker', name='talker')
sl.node(package='composition', plugin='Listener', name='listener')
return sl.launch_description()
Events and parameters
This example file is another way to write the event launch example. If does a little more work and is a little smarter, as the passed new_background_r
is applied as soon as it has a valid value.
auto sim time
Here we run Gazebo and force all other nodes to use_sim_time:=True
, unless this file is included from another one with use_sim_time:=False
.
This is unlikely as this launch file spawns a simulator.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
# all nodes in this launch file will use_sim_time:=True
sl = SimpleLauncher(use_sim_time=True)
# run Gazebo + clock bridge
sl.gz_launch(<path/to/some/sdf/world>, '-r')
sl.create_gz_clock_bridge()
# run other nodes with sim time
return sl.launch_description()
Robot description and conditionnal Gazebo bridge
The file below only runs by default a robot_state_publisher
with use_sim_time:=False
.
However, if it is included from another file with use_sim_time:=True
then it also spawns the robot into Gazebo and runs two bridges for joint states and pose.
from simple_launch import SimpleLauncher, GazeboBridge
def generate_launch_description():
sl = SimpleLauncher(use_sim_time=False)
# namespace is a launch argument, not a Python string
sl.declare_arg('robot', default_value = 'robot1')
robot = sl.arg('robot')
with sl.group(ns = robot):
# robot_state_publisher is always run
sl.robot_state_publisher('my_description', 'my_robot.xacro')
with sl.group(if_condition = sl.sim_time):
# only execute this group if use_sim_time was set to True
# spawn in Gazebo at default pose if not already here
sl.spawn_gz_model(robot)
# create a bridge for joint states @ /world/<world>/model/<robot>/joint_state
# note the relative ROS topic 'joint_states' that is actually namespaced
gz_js_topic = GazeboBridge.model_prefix(robot)/'joint_state'
js_bridge = GazeboBridge(gz_topic = gz_js_topic,
ros_topic = 'joint_states',
msg = 'sensor_msgs/JointState',
direction = GazeboBridge.gz2ros)
# pose publisher bridge @ /model/<robot>
pose_bridge = GazeboBridge('/model'/robot/'/pose',
'pose_gt', 'geometry_msgs/Pose', GazeboBridge.gz2ros)
# create bridge node with these two topics with default name gz_bridge
sl.create_gz_bridge([js_bridge, pose_bridge])
return sl.launch_description()
Full Gazebo simulation
The file example/gazebo/gazebo_launch.py
runs a basic simulation of a turret robot with a camera, also displayed in RViz.
ros2 launch simple_launch gazebo_launch.py
You can move the robot around with a joint velocity setpoint (std_msgs/Float64
) on /turret/joint#
and see the simulated camera on /turret/image
.
I want more examples
Other self-contained examples (and slides) have been used to teach the ROS 2 launch file system and the nav stack.
Various aspects of the launch systen are shown in the anf_launch package.
A simple tutorial on Nav2
using simple_launch
is available in the anf_nav package.
Changelog for package simple_launch
1.10.1 (2024-07-05)
- check for gz/ign executable being available
- gz_world_tf + better guess on Gz vs Ign
- Contributors: Olivier Kermorgant
1.10.0 (2024-06-16)
- scope_included_files to include other launch files in a Group and avoid changing my scope
- remove dead code about prefixing gz plugins
- forward sim_time even for nodes that load a parameter file
- lazy GazeboBridge
- Contributors: Olivier Kermorgant
1.9.2 (2024-03-25)
- Gazebo basic example: launch SDF world + spawn from xacro
- remove dead code related to Gazebo.
- sl.arg returns a SimpleSubstitution to allow concatenation
- auto-detect Gazebo world name, allows running the simulation + spawn models in the same launch file
- Type debug on String being Iterable
- better handling of non-string choices in argument declaration
- more robust to various gz/ros combinations
- Contributors: Olivier Kermorgant
1.9.1 (2024-02-20)
- simplify + debug logic of SimpleSubstitution divisions
- image instead of /image to be detected as an image topic
- remove auto_sim_time function
- more robust to various combinations of ROS and Gazebo
- default Gazebo is still ignition Fortress, better error message about GZ_VERSION
- add new bridges for Gazebo
- Contributors: Olivier Kermorgant
1.9.0 (2023-11-23)
- update documentation
- warnings/errors on misuse of GazeboBridge
- move example executable to share directory
- dict cannot be updated with | in Foxy, fallback to dict.update
- absolute container name when loading in existing container
- py_eval can now handle conditions
- Contributors: Olivier Kermorgant
1.8.0 (2023-11-20)
- sync documentation and examples
- when instead of after for events
- scoped events
- add event wrapper
- Contributors: Olivier Kermorgant
1.7.2 (2023-10-02)
- simplify logic of try_perform
- Merge pull request #5 from okvik/devel Fix string-valued launch argument substitution
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant, Viktor Pocedulic
- slight refactor to prepare wrapping Delays
- Contributors: Olivier Kermorgant
1.7.1 (2023-05-16)
- list[] -> List[] for type hints in 20.04
- detail on __ns for services
- add service call at launch
- Contributors: Olivier Kermorgant
1.7.0 (2023-02-22)
- GazeboBridge creates a camera_info topic for all bridged image topics
- Contributors: Olivier Kermorgant
1.6.2 (2023-01-23)
- add .rviz shortcut, clean Python scripts
- Contributors: Olivier Kermorgant
1.6.1 (2022-10-10)
- fix bug in robot_state_publisher with raw URDF
- Contributors: Olivier Kermorgant
1.6.0 (2022-10-06)
- check use_sim_time versus a parameter file
- resolve any builtin type as Substitution, not only text
- improve documentation
- Gazebo + humble compat
- OpaqueFunction wrapper and SimpleSubstitution
- switch to CMake to avoid deprecation messages
- more spawn_gz
- Contributors: Olivier Kermorgant
1.5.0 (2022-08-26)
- allow spawning a Gz model from file
- parameters are list of dict
- allow substitution for topics in ros_ign_image bridge
- Gazebo bridge handles invalid ROS topics through yaml config file. Image bridges are automatically run through ros_ign_image
- better handling of gazebo spawn pose
- Contributors: Olivier Kermorgant
1.4.1 (2022-06-01)
- more handling of param types
- Contributors: Olivier Kermorgant
1.4.0 (2022-06-01)
- use Gazebo instead of Ignition
- better type comprehension
- Contributors: Olivier Kermorgant
1.3.1 (2022-05-02)
- use underscores in setup.cfg
- typo in included_launch example
- Merge pull request #4 from yushijinhun/patch-1 Add package & executable parameter to container
- [readme] add doc for container.package
- Add package & executable param to container This allows the user to use a component container implementation other than [component_container]{.title-ref}, such as [component_container_isolated]{.title-ref} and [component_container_mt]{.title-ref}.
- Contributors: Haowei Wen, Olivier Kermorgant
1.3.0 (2022-02-03)
- more use_sim_time: constructor + warning on 'auto'
- auto_sim_time can be forced instead of checking /clock
- Contributors: Olivier Kermorgant
1.2.1 (2022-01-24)
- add Ignition support
- Contributors: Olivier Kermorgant
1.2.0 (2021-11-02)
- make it clearer for the prefix_gz_plugins param
- Contributors: Olivier Kermorgant
1.1.0 (2021-09-25)
- add capacity to prefix and namespace Gazebo-published messages, as an alternative to using Gazebo namespaces that also remap /tf
- Contributors: Olivier Kermorgant
1.0.6 (2021-09-22)
- node arguments is a raw list and accepts substitutions
- Contributors: Olivier Kermorgant
1.0.5 (2021-09-22)
- automagically convert to expected type for node parameters, remappings, launch arguments
- Contributors: Olivier Kermorgant
1.0.4 (2021-09-03)
- some Python2 legacy bugs
- Contributors: Olivier Kermorgant
1.0.3 (2021-04-17)
- solve typo in node_args
- better handling of node arguments in nested lists
- bug fixes around Substitutions
- Merge pull request #1 from oKermorgant/master deduce executable from package name if needed
- Contributors: Olivier Kermorgant
1.0.2 (2020-12-08)
- composition with existing container
- Contributors: Olivier Kermorgant
1.0.1 (2020-10-12)
- PythonExpression shortcut
- xacro args now take substitution args
- add LoadComposableNode feature for existing containers
- add name_join and path_join to combine raw str and Substitution stuff
- first commit
- Contributors: Olivier Kermorgant