[Discuss-gnuradio] Recording Probe Rate or other Messages

I have a flowgraph in which I can probe the rate using the "Probe Rate" block and I connect it to the "Message Debug" block as such:

self.msg_connect((self.blocks_probe_rate_0, 'rate'), (self.blocks_message_debug_0, 'print'))

self.connect((self.blocks_file_source_0, 0), (self.blocks_probe_rate_0, 0))

Instead of sending the rate to the terminal to read, I would like to send it to a file for post processing. How can I do this in python? I'd also be fine getting the average rate over some time period and returning a single value.

Thanks!