Python ctypes: How do I flush output from stderr?

I've written some function callbacks using python's ctypes to access functions in a DLL. The code used to build that DLL has some debugging print statements in it using fprintf to stderr. However, when I run my python code, I don't see that output to stderr consistently. Only rarely I will see it flush the output from stderr to the console that I'm using. I've开发者_运维技巧 tried running it with "python -u foo.py", but that doesn't help either. Any suggestions?

It's all the same stderr.

sys.stderr.flush()