Making sure a Python script with subprocesses dies on SIGINT

The subprocess is by default part of the same process group, and only one can control and receive signals from the terminal, so there are a couple of different solutions.

Setting stdin as a PIPE (in contrast to inheriting from the parent process), this will prevent the child process from receiving signals associated to it.

subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)

Detaching from the parent process group, the child will no longer receive signals

def preexec_function():
    os.setpgrp()

subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, preexec_fn=preexec_function)

Explicitly ignoring signals in the child process

def preexec_function():
    signal.signal(signal.SIGINT, signal.SIG_IGN)

subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, preexec_fn=preexec_function)

This might however be overwritten by the child process.