[rospy] simultaneous subscribe at a given frequency

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It is not possible to subscribe at a given frequency, you have to filter the incoming messages yourself:

If the topics have to be synchronized, use a TimeSynchronizer for your subscription. In your callback, check the last time you stored the messages and if it is more than 2 seconds ago, store again and store the timestamp.

If your topics do not have to be synchronized and you just want the output to be logged to a textfile you can use throttle to republish your topic at the desired rate and rostopic for logging:

rosrun topic_tools throttle messages /topic 2.0
rostopic echo -p /topic_throttled > topiclog.txt