PuDB is a full-screen, console-based visual debugger for Python.

Its goal is to provide all the niceties of modern GUI-based debuggers
in a more lightweight and keyboard-friendly package. PuDB allows you
to debug code right where you write and test it--in a terminal. If
you've worked with the excellent (but nowadays ancient) DOS-based
Turbo Pascal or C tools, PuDB's UI might look familiar.

A simple, but useful, illustrated example page:

http://heather.cs.ucdavis.edu/~matloff/pudb.html