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 alrea

Answer 1

remote-pdb can be used to debug sub-processes. After installation, put the following lines in the code you need to debug:

import remote_pdb
remote_pdb.set_trace()

remote-pdb will print a port number which will accept a telnet connection for debugging that specific process. There are some caveats around worker launch order, where stdout goes when using various frontends, etc. To ensure a specific port is used (must be free and accessible to the current user), use the following instead:

from remote_pdb import RemotePdb
RemotePdb('127.0.0.1', 4444).set_trace()

remote-pdb may also be launched via the breakpoint() command in Python 3.7.