pycodestyle

pycodestyle (formerly pep8) is a tool to check your Python code against some of the style conventions in PEP 8. This package used to be called pep8 but was renamed to pycodestyle to reduce confusion. Plugin architecture, adding new checks is easy. Parseable output, jump to error location in your editor. Just one Python file, requires only stdlib. You can use just the pycodestyle.py file for this purpose. Comes with a comprehensive test suite. There's also a package for Debian/Ubuntu, but it's not always the latest version. You can also make pycodestyle.py show the source code for each error, and even the relevant text from PEP 8. Or you can display how often each error was found.