PyMOTW: argparse – Command line option and argument parsing.

The argparse module was added to Python 2.7 as a replacement for optparse. The implementation of argparse supports features that would not have been easy to add to optparse, and that would have required backwards-incompatible API changes, so a new module was brought into the library instead. optparse is still supported, but is not likely to receive new features.

Read more at pymotw.com: argparse