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Hi, everyone.
Like the title, I want to show topics using python in ROS2.
First I thought use a ros2 topic list command through a subprocess module of python, but If possible I want to use a official ros2cli package of python.
Please, could anyone tell me how to use a ros2cli package?
Thank you everyone for telling me good information, I implemented a sample code below using get_topic_names_and_types.
### `sample_to_show_topic_list.py` ###
import rclpy
from rclpy.node import Node
def get_topic_list():
node_dummy = Node("_ros2cli_dummy_to_show_topic_list")
topic_list = node_dummy.get_topic_names_and_types()
node_dummy.destroy_node()
return topic_list
rclpy.init()
topic_list = get_topic_list()
for info in topic_list:
print(info[0])
rclpy.shutdown()
Execute this code, and get following output in the terminal.
$ ros2 topic pub --rate 1 hoge std_msgs/msg/String "{data: "hoge"}" # publish a string
$ python3 sample_to_show_topic_list.py # show topic list
/hoge
/parameter_events
/rosout
You can use the python client library and ask for the topics for each node: using get_publisher_names_and_types_by_node iterating through each node on the system which is available via get_node_names
Both are documented in the rclpy Node API: http://docs.ros2.org/latest/api/rclpy...
We don't appear to have the straight API for asking for the list from all nodes on the system, which I think would be a nice enhancement PR if someone would wish to do that.
You can look how the ros2cli is make it. But subprocess is the cleaner way. Through the ros2cli you can extend the ros2 cmd list. But it is not used for the other way around
i mean it by the philosophy of unix, use a set small tools to complete a complex task.
and not reinvent the wheel. but if the node api has this call it is also ok.
Asked: 2021-01-05 00:19:05 -0500
Seen: 2,843 times
Last updated: Jan 06 '21
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