How to obtain the msg format of a topic on runtime?

asked 2011-04-28 06:31:23 -0600

Poseidonius

427 ●31 ●42 ●51

updated 2014-01-28 17:09:36 -0600

ngrennan
1 ●1 ●1

Hi,

I need to implement a dynamic subscription mechanism, that monitors the available topics. Firstly it takes a view to the msg format of new topics and subscribes to this one depending on a special data format. The first step, to know the current available topics works fine with the following code:

available_topics_old=[]
def monitor():
   while not rospy.is_shutdown():
      master = rosgraph.masterapi.Master('/rostopic')
      available_topics = master.getPublishedTopics('/') 
      new_topics=[]
      for topic in available_topics:
         if not topic in available_topics_old:
            new_topics.append(topic)
      if new_topics:
          # here I need to know the format(file) of the assigned msg
   rospy.sleep(1.0)

How can I get the msg format of the topic?

Best wishes from Germany

Poseidonius

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answered 2011-04-28 08:01:41 -0600

kwc
12244 ●54 ●90 ●132 http://kwc.org/

These are unofficial/volatile APIs, but you can look at how they introspect on the graph to pull the data out (most of this can be done with the masterapi or filesystem operations):

import roslib.message
import rostopic
import rosmsg

type_name = rostopic.get_topic_type('/rosout', blocking=False)[0]
if type_name:
    message_class = roslib.message.get_message_class(type_name)
    message_text = rosmsg.get_msg_text(type_name)
    full_message_text = message_class._full_text

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answered 2011-04-29 04:41:25 -0600

Poseidonius

427 ●31 ●42 ●51

Very nice, that's the commands I looked for!

Thank you very much

Poseidonius

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@Poseidonius Please mark the best answer by clicking the check mark next to it, so others know the question is answered. I"ve done it for you in this case.

tfoote ( 2011-04-29 08:49:02 -0600 )edit

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How to obtain the msg format of a topic on runtime?

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