Snippet for signal handling in Python (useful for monitoring)

signalhandling.py

import signal
import os
import readline

from pprint import pprint

def handle_shell(signal, frame):
    frames = []
    
    while frame:
        frames.append({'locals':frame.f_locals, 'globals': frame.f_globals})
        frame = frame.f_back
    
    print("You can acess the frames via the `frames` local variable")
    try:
        import IPython; IPython.embed()
    except:
        import code
        code.interact(local=dict(globals(), **locals()))
        

def handle(signal, frame):
    i = 0
    while frame:
        print()
        print('-'*80)
        print("frame {}".format(i).center(80))
        print('-'*80)
        print('--- locals')
        pprint(frame.f_locals)
        print('--- globals')
        pprint(frame.f_globals)

        # walk up the call frame
        frame = frame.f_back
        i -= 1

signal.signal(signal.SIGUSR1, handle)
signal.signal(signal.SIGUSR2, handle_shell)

# --- code
g = 'i am global'
def process():
    a = 1
    b = 2
    c = 3
    l = 'i am local'
    while True:
        a += b + 2*(c - b)
        c  = a - a/2
        b  = b+2

if __name__ == '__main__':
    pid = os.getpid()
    print("PID: %d" % pid)
    print("kill -USR1 %d # to print out stack frames" % pid)
    print("kill -USR2 %d # to open an interactive Python shell" % pid)
    process()