Pyflakes is a simple program which checks Python source files for errors. It is
similar to PyChecker in scope, but differs in that it does not execute the 
modules to check them. This is both safer and faster, although it does not 
perform as many checks. Unlike PyLint, Pyflakes checks only for logical errors 
in programs; it does not perform any checks on style.

WWW: https://launchpad.net/pyflakes