Python ValueError: bad marshal data

I have been programming for many years but consider myself to be somewhat of an "empirical programmer", i.e. I am almost entirely self-taught. As a result, I sometimes come across new and exciting error messages that I have neither encountered nor understand. I have just had one such error:

ValueError: bad marshal data

This was associated with an import command for several modules.

I still don't know what bad marshal data is (it sounds like it should be something to do with Wild West movies) but, fortunately, I have found an easy fix: just delete all the compiled *.pyc files. Missing ones are remade when you run your python code anyway. Problem solved without any need to delve into the murky underworld of bad marshals.