The pdb (for 'p'ython 'd'e'b'ugger) module enables you to step through executing code, pausing at each line, or running to pre-set breakpoints. Docs are at http://python.org/doc/2.4.1/lib/module-pdb.html. If you're on Windows, make sure that you run python and not pythonw, or you won't see the output.

pdb is certainly low level, but after using it a bit you should be able to figure out how to get around pretty well. If you have a section of code you want to step through, add these two lines:

 import pdb
 pdb.set_trace()

That's the equivalent to the VFP SET STEP ON command, for those of you who are VisualFoxPro users. From that point, execution halts until you tell it how to proceed. The main keys and their Fox equivalents are:

Any time execution stops, you can issue Python commands to check the values of variables, properties, etc., or even change them.