Debugging Python Scripts inside other processes

[A. Klingenstein]

I embedded Python in a Windows C++ program. Now I want to debug my 
embedded scripts which of course won't run in any IDE process. 
Commercial IDEs like WingIDE can attach to external processes by 
importing a module in the scripts. Is there a debugger capable of this 
which is Free or Open Source?

What I need are the following things:
- runs in Windows
- single stepping
- variable watches
- breakpoints

Just the typical debugger stuff.

Alex