rospy: throttling logmessage rate?

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Update (2016-06-03): a recent PR added support for throttled logging in Python. See wiki/rospy/Overview/Logging - Logging Periodically.

Answering my own question:

It would seem this is rather difficult to implement in Python. The ROS_*_THROTTLE(..) macro can exploit some features of C/C++ (variable scoping, static variables): state information is inserted for every individual invocation of the macro (see ros/console.h#L422-433). This makes it possible to easily support multiple calls with different period arguments, without resorting to for instance __FILE__ __LINE__ trickery (which wouldn't work anyway).

Python does not support this, and would require a different approach. After some experimentation, adding runtime, per-invocation state information seems hard to implement, at least in a way supported by the many runtimes in existence and/or Python 3+. One approach could be to use a (object_id, function_name, line_nr) tuple to uniquely identify an invocation. Unfortunately it seems impossible to retrieve this information without the use of functionality not supported everywhere (inspect and / or sys._getframe()). This would also shift the responsibility of keeping track of previous invocations to the log*throttle(..) implementations.