The package launch-generator is a tool to easily generate launch descriptions for ROS 2.
It is based on the launch and launch_ros packages.
pip install launch-generatorGenerator is the main class of the package. It is used to generate launch descriptions.
It can add some actions with the add_* methods and generate the launch description with the generate_launch_description method.
add_* methods arguments are the same as the original basically.
add_group() and add_container() methods return a generator object that can be used to add internal actions to the group or container.
from launch import LaunchDescription
import launch_generator
def generate_launch_description() -> LaunchDescription:
gen = launch_generator.Generator()
# Add launch arguments
arg_configuration = gen.add_arg('arg_name', 'default_value')
# Add nodes and use the launch arguments
node = gen.add_node('executable_name', 'package_name', name=arg_configuration)
# Include other launch files
include = gen.include_launch('package_name', 'launch/file/path.launch.py')
# Add group
group = gen.add_group('namespace')
# Add nodes to group
group.add_node('executable_name', 'package_name')
return LaunchDescription(gen.generate_launch_description())launch_ros
from launch import LaunchDescription
from launch_ros.actions import *
from launch_ros.substitutions import *
...launch_generator
from launch import LaunchDescription
import launch_generatorlaunch_ros
# declare argument
arg = launch.actions.DeclareLaunchArgument(name,
default_value=default_value,
description=description,
choices=choices)
# use argument
Node(
...
parameters=[{'param_name': launch.substitutions.LaunchConfiguration(name)}]
)
# add argument to launch description
return LaunchDescription([arg, ...])launch_generator
arg = gen.add_arg(name, default_value, description, choices)
Node(
...
parameters=[{'param_name': arg}]
)
return LaunchDescription(gen.generate_launch_description())launch_ros
Node(
package=package,
executable=executable,
name=name,
namespace=namespace,
parameters=parameters,
remappings=remappings,
arguments=arguments,
**kwargs
)
# add node to launch description
return LaunchDescription([node, ...])launch_generator
node = gen.add_node(executable, package, name, namespace, parameters=parameters, remappings=remappings, ros_arguments=arguments, **kwargs)
return LaunchDescription(gen.generate_launch_description())launch_ros
package_path = FindPackageShare('package_name').find('package_name')
launch_file_path = os.path.join(package_path, 'launch', 'file_name.launch.py')
include = IncludeLaunchDescription(
launch.launch_description_sources.PythonLaunchDescriptionSource(launch_file_path),
)
# add include to launch description
return LaunchDescription([include, ...])launch_generator
gen.add_include_launch_description('package_name', 'launch/file_name.launch.py')
return LaunchDescription(gen.generate_launch_description())launch_ros
group = GroupAction(
actions=[
PushRosNamespace(
namespace=namespace,
),
Node(
...
),
Node(
...
),
]
)
# add group to launch description
return LaunchDescription([group, ...])launch_generator
group = gen.add_group(namespace)
group.add_node(...)
group.add_node(...)
return LaunchDescription(gen.generate_launch_description())launch_ros
container = ComposableNodeContainer(
name=name,
namespace=namespace,
package='rclcpp_components',
executable='component_container',
composable_node_descriptions=[
ComposableNode(...),
ComposableNode(...),
],
)
# add container to launch description
return LaunchDescription([container, ...])launch_generator
container = gen.add_container(name, namespace)
container.add_composable_node(...)
container.add_composable_node(...)
return LaunchDescription(gen.generate_launch_description())launch_ros
node = ComposableNode(
package=package,
plugin=plugin,
name=name,
namespace=namespace,
parameters=parameters,
remappings=remappings,
extra_arguments=extra_arguments,
)
return LaunchDescription([node, ...])launch_generator
node = container.add_composable_node(package, plugin, name, namespace, parameters, remappings, extra_arguments)
return LaunchDescription(gen.generate_launch_description())launch_ros
load_composable_nodes = LoadComposableNodes(
target_container='target_container_name',
composable_node_descriptions=[
ComposableNode(...),
ComposableNode(...),
],
)
return LaunchDescription([load_composable_nodes, ...])launch_generator
load_composable_nodes = gen.add_load_composable_nodes('target_container_name', [
gen.add_composable_node(...),
gen.add_composable_node(...),
])
return LaunchDescription(gen.generate_launch_description())launch_ros
register_event_handler = RegisterEventHandler(
event_handler=OnProcessExit(
target_action=target_node,
on_exit=[other_node],
),
)
return LaunchDescription([register_event_handler, ...])launch_generator
on_exit = gen.add_register_event_handler(target_node, launch_generator.EventTriggerType.ON_EXIT)
on_exit.add_action(executable, package, name)
return LaunchDescription(gen.generate_launch_description())launch_ros
timer = RosTimer(
period=period,
actions=[
Node(
...
),
Node(
...
),
]
)
return LaunchDescription([timer, ...])launch_generator
timer = gen.add_ros_timer(period)
timer.add_node(...)
timer.add_node(...)
return LaunchDescription(gen.generate_launch_description())launch_ros
set_parameter = SetParameter(
name=name,
value=value,
)
return LaunchDescription([set_parameter, ...])launch_generator
gen.add_set_parameter(name, value)
return LaunchDescription(gen.generate_launch_description())launch_ros
package_path = FindPackageShare('package_name').find('package_name')
config_file_path = os.path.join(package_path, 'config', 'file_name.yaml')
set_parameter_file = SetParameterFile(config_file_path)
return LaunchDescription([set_parameter_file, ...])launch_generator
gen.add_set_parameter_file('package_name', 'config/file_name.yaml')
return LaunchDescription(gen.generate_launch_description())launch_ros
set_remap = SetRemap(
src=src_topic,
dst=dst_topic,
)
return LaunchDescription([set_remap, ...])launch_generator
gen.add_set_remap(src_topic, dst_topic)
return LaunchDescription(gen.generate_launch_description())launch_ros
set_env = SetEnvironmentVariable(
name=name,
value=value,
)
return LaunchDescription([set_env, ...])launch_generator
gen.add_set_environment_variable(name, value)
return LaunchDescription(gen.generate_launch_description())add_action() supports all the entities of launch and launch_ros packages.
launch_ros
ns = PushRosNamespace(
namespace=namespace,
)
return LaunchDescription([ns, ...])launch_generator
gen.add_action(PushRosNamespace(namespace))
return LaunchDescription(gen.generate_launch_description())condition() is a function to create IfCondition or UnlessCondition object.
arg = gen.add_arg(name, default_value, description, choices)
# basic usage
gen.add_node('executable_name', 'package_name',
condition=launch_generator.condition(arg)) # the node is launched only if arg is 'True' or 'true'
# reverse condition
gen.add_node('executable_name', 'package_name',
condition=launch_generator.condition(arg, reverse=True)) # the node is launched only if arg is 'False' or 'false'
# python expression can be used
gen.add_node('executable_name', 'package_name',
condition=launch_generator.condition([arg, '< 10'])) # the node is launched only if arg is less than 10
arg2 = gen.add_arg(name, default_value, description, choices)
# multiple conditions can be used
gen.add_node('executable_name', 'package_name',
condition=launch_generator.condition([arg, '< 10 or ', arg2])) # the node is launched only if arg is less than 10 or greater than 20load_param_file() is a function to load a yaml file to parameter dictionary.
The function can replace the value of parameters written in the form of $(arg arg_name) like subst_value of ROS1 with LaunchConfiguration(arg_name).
Example of yaml file:
node_name:
ros__parameters:
param1: $(arg arg_name)
param2:
sub1: prefix_$(arg arg_name)
sub2: $(arg arg_name)_suffix
sub3: $(arg arg_name)_$(arg_name2)arg = gen.add_arg('arg_name', 'default_value')
arg2 = gen.add_arg('arg_name2', 'default_value')
param_dict = launch_generator.load_param_file('package_name', 'config/file_name.yaml')
# param_dict = {
# 'node_name': {
# 'ros__parameters': {
# 'param1': launch.substitutions.LaunchConfiguration('arg_name'),
# 'param2': {
# 'sub1': ['prefix_', launch.substitutions.LaunchConfiguration('arg_name')],
# 'sub2': [launch.substitutions.LaunchConfiguration('arg_name'), '_suffix'],
# 'sub3': [launch.substitutions.LaunchConfiguration('arg_name'), '_', launch.substitutions.LaunchConfiguration('arg_name2')],
# }
# }
# }
# }
gen.add_node('executable_name', 'package_name', parameters=[param_dict['node_name']['ros__parameters']])
return LaunchDescription(gen.generate_launch_description())
