Typing `C-c p d b` in my Emacs inserts this macro:

import sys; sys.stdout = sys.__stdout__; import ipdb; ipdb.set_trace()

All the benefits of a Lisp REPL and a Smalltalk debugging environment in a language people actually use. Tab-completion, dumps, breakpoints, testing assumptions/data, running arbitrary code inside a specific environ...the works.

I can use it in my virtualenvs without having to explain to an IDE what a virtualenv, a running test in Nose, a normal script, or a running web server. It's normal code so I can wrap the trace in a condition or whatever else I want.