By default, Pdb and other instances of Cmd complete names for their commands. However in the context of pdb, I think it is more useful to complete identifiers and keywords in its current scope than to complete names of commands (most of which have single letter abbreviations). I believe this makes pdb a far more usable introspection tool.

I have discussed this proposal on the python-ideas list:
http://mail.python.org/pipermail/python-ideas/2007-January/000084.html

This patch implements the following:
  - creates an rlcompleter instance on Pdb if readline is available
  - adds a 'complete' method to the Pdb class. The only difference with rlcompleter's default behaviour is that is also updates rlcompleter's namespace to reflect the current local and global namespace, which is necessary because pdb changes scope as it steps through a program

This is a patch against python/Lib/pdb.py rev. 51745