python-gflags is the Python equivalent of google-gflags, a Google command-line flag implementation for C++. It is intended to be used in situations where a project wants to mimic the command-line flag handling of a C++ app that uses google-gflags, or for a Python app that, via swig or some other means, is linked with a C++ app that uses google-gflags.
The gflags package contains a library that implements commandline flags processing. As such it's a replacement for getopt(). It has increased flexibility, including built-in support for Python types, and the ability to define flags in the source file in which they're used. (This last is its major difference from OptParse.)
Documentation is at the top of gflags.py.