Is there a way to attach a debugger to a multi-threaded Python process?

Question

I\'m trying to debug a deadlock in a multi-threaded Python application after it has locked up. Is there a way to attach a debugger to inspect the state of the process?

Answer 1

This can be used as a dead simple "remote" debugger:

import sys
import socket
import pdb

def remote_trace():
    server = socket.socket()
    server.bind(('0.0.0.0', 12345))
    server.listen()
    client, _= server.accept()
    stream = client.makefile('rw')
    sys.stdin = sys.stdout = sys.stderr = stream
    pdb.set_trace()

remote_trace()

# Execute in the shell: `telnet 127.0.0.1 12345`

On Windows it's easier to use Netcat instead of Telnet (which will also work on linux).