python debugging question

[diffuser78 at gmail.com]

I am a python newbie. I have writen some 500 lines of code. There are 4
classes and in all 5 files.

Now, I am trying to run the program. I am getting wrong values for the
simulation results.
Is there any debugging facilities in python which would let me go step
by step and check the values of the variables at every step. I have
done something like this in MS Visual Stdio 6.0 sometime back.

For python, I am using SPE.

what is a good way of debugging such large and iterative programs ? Any
tips.

Every help is appreciated.

Thanks