For example: python functions shall have a docstring unless trivial. For external api functions on a class, there must be at least one example. etc etc. Plus, this makes working in ipython really nice!
You could always use a tool like Danger (http://danger.systems/) to inspect your code and warn you when code has been updated, but comments nearby have not been.
This is what code coverage analysis/metrics try to address.
> You could always use a tool like Danger (http://danger.systems/) to inspect your code and warn you when code has been updated, but comments nearby have not been.
I'd worry about tuning out said warnings after too many false positives. Comments regular enough to not generate too many false positives can generally be turned into real syntax of some description.
In terms of developer resources, the act of doing updating the comments is cheap, but the act of making sure it gets done (in a systematic way) is comparatively expensive.