How to attach debugger to a python subproccess?

Question

I need to debug a child process spawned by multiprocessing.Process(). The pdb degugger seems to be unaware of forking and unable to attach to already running processes.

Are there any smarter python debuggers which can be attached to a subprocess?

Answer 1

I've been searching for a simple to solution for this problem and came up with this:

import sys import pdb  class ForkedPdb(pdb.Pdb):     """A Pdb subclass that may be used     from a forked multiprocessing child      """     def interaction(self, *args, **kwargs):         _stdin = sys.stdin         try:             sys.stdin = open('/dev/stdin')             pdb.Pdb.interaction(self, *args, **kwargs)         finally:             sys.stdin = _stdin 

Use it the same way you might use the classic Pdb:

ForkedPdb().set_trace() 

Answer 2

Winpdb is pretty much the definition of a smarter Python debugger. It explicitly supports going down a fork, not sure it works nicely with multiprocessing.Process() but it's worth a try.

For a list of candidates to check for support of your use case, see the list of Python Debuggers in the wiki.