I wish I could provide a simple sample case that occurs using standard library code, but unfortunately it only happens when using one of our in-house libraries that in turn is built on top of sql alchemy.
Basically, the problem is that this break command:
(Pdb) print sqlalchemy.engine.base.__file__
(Pdb) break /prod/eggs/SQLAlchemy-0.5.5-py2.5.egg/sqlalchemy/engine/base.py:946
Is just being totally ignored, it seems, by pdb. As in, even though I am positive the code is being hit (both because I can see log messages, and because I've used sys.settrace to check which lines in which files are being hit), pdb is just not breaking there.
I suspect that somehow the use of an egg is confusing pdb as to what files are being used (I can't reproduce the error if I use a non-egg'ed library, like pickle; there everything works fine).
It's a shot in the dark, but has anyone come across this before?