Why are the methods sys.exit(), exit(), raise SystemExit not working?

Question

I need an alternative to kill the python script while inside a thread function. My intention is killing the server when the client enters a 0... Is this not working because the threads haven't been terminated? Here is my code:

socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM);
print 'Socket created'

try:
    socket.bind((HOST, PORT))
except socket.error, message:
    print 'Bind statement failed. ERROR: ' + str(message[0]) + ' Message: ' +    message[1]
    sys.exit()

print 'Socket Binding Successful'

socket.listen(10)
print 'Socket is currently listening'


def clientThread(connection):
    while 1:
        data = connect.recv(1024)
        try:
            quit = int(data)
        except:
            quit = 3
        if quit == 0:
            print 'Closing the connection and socket...'
            connect.close()
            socket.close()
            sys.exit(); //Alternative needed here...
            break
        reply = 'Ok....' + data
        if not data:
            break
        connect.sendall(reply)


while 1: #forever loop
    connect, address = socket.accept()
    print 'Just connected with ' + address[0] + ' : ' + str(address[1])
    start_new_thread(clientThread, (connect,))

socket.close()

Tragedy

Answer 1

The problem is that all sys.exit() does is raise SystemExit. Since this happens in a worker thread, the effect is to stop that thread (exceptions don't propagate across threads).

You could trying signalling to the main thread that the script needs to terminate, either though some mechanism of your own, or by calling thread.interrupt_main().

For a sledgehammer approach, call os._exit().

Clippard

I import os, but when trying 'os._exit()' I get the error: Traceback (most recent call last): File "server.py", line 35, in clientThread os._exit(); NameError: global name 'os' is not defined – Tragedy

@CSGamer: Where did you add the import? Are you sure you don't have a typo? Because there's no reason that shouldn't work. – Airmail

Here are my imports at the top: import os import sys from thread import * – Tragedy

Also, after sending the interrupt to main, there is no keyboard interrupt received after interrupt_main() The weird thing is I only receive the keyboard interrupt after trying to reconnect to the server... – Tragedy

@CSGamer: I think with your current code, os._exit() is the only feasible alternative. However, I have no idea what's happening to your imports. – Clippard

I realized why os._exit() wasn't working. I didn't have any parameter... Now using 1, it works properly! Thanks – Tragedy

Answer 2

You can just raise SystemExit but that seems really harsh. Maybe some means of co-operative threading would work (ie: a queue with a sentinel)

Ursulina

raise SystemExit doesn't kill the script either. Only the thread that calls it... – Tragedy

That's because raise SystemExit and and sys.exit are basically the same – Fidelia