With modern revision control available, there is no reason to save
commented-out code to your repository. eradicate helps cleans up existing junk
comments. It does this by detecting block comments that contain valid Python
syntax that are likely to be commented out code. (It avoids false positives
like the sentence this is not good, which is valid Python syntax, but is
probably not code.)

Homepage:
https://github.com/myint/eradicate
