PyFlakes a Lint-like tool for Python, like PyChecker. It is focused on
identifying common errors quickly without executing Python code.

Its primary advantage over PyChecker is that it is fast. You don't
have to sit around for minutes waiting for the checker to run; it runs
on most large projects in only a few seconds.

The two primary categories of defects reported by PyFlakes are:
* Names which are used but not defined or used before they are defined
* Names which are redefined without having been used 

These can each take many forms. For example, PyFlakes will tell you
when you have forgotten an import, mistyped a variable name, defined
two functions with the same name, shadowed a variable from another
scope, imported a module twice, or two different modules with the same
name, and so on.