How to send a signal to the main thread in python without using join?

Question

I Am trying to send a signal from a child thread to the main thread in a multi-threaded program (cannot use multi-processes). Unfortunately even after exhausting all the rea

Answer 1

Signals and threads really, really don't play nice together.

Consider use an Event or other synchronization mechanism. The following example creates an 'event' object, then passes it to two threads. One waits for two seconds, then signals the other to print out a message then exit.

source

import threading, time

def flagger_thread(event):
    """
    wait for two seconds, then make 'event' fire
    """
    time.sleep(2)
    event.set()

def waiter_thread(event):
    print("Waiting for event")
    if event.wait(5):
        print("event set.")
    else:
        print("Timed out.")

stop_event = threading.Event()
threading.Thread(target=flagger_thread, args=[stop_event]).start()
threading.Thread(target=waiter_thread, args=[stop_event]).start()

# wait for all threads to exit
for t in threading.enumerate():
    if t != threading.current_thread():
        t.join()

output

Waiting for event
event set.