How to stop an infinite loop safely in Python?

What you need to do is catch the interrupt, set a flag saying you were interrupted but then continue working until it's time to check the flag (at the end of each loop). Because python's try-except construct will abandon the current run of the loop, you need to set up a proper signal handler; it'll handle the interrupt but then let python continue where it left off. Here's how:

import signalimport time   # For the demo onlydef signal_handler(signal, frame):    global interrupted    interrupted = Truesignal.signal(signal.SIGINT, signal_handler)interrupted = Falsewhile True:    print("Working hard...")    time.sleep(3)    print("All done!")    if interrupted:        print("Gotta go")        break

Notes:

1. Use this from the command line. In the IDLE console, it'll trample on IDLE's own interrupt handling.

2. A better solution would be to "block" KeyboardInterrupt for the duration of the loop, and unblock it when it's time to poll for interrupts. This is a feature of some Unix flavors but not all, hence python does not support it (see the third "General rule")

3. The OP wants to do this inside a class. But the interrupt function is invoked by the signal handling system, with two arguments: The signal number and a pointer to the stack frame-- no place for a self argument giving access to the class object. Hence the simplest way to set a flag is to use a global variable. You can rig a pointer to the local context by using closures (i.e., define the signal handler dynamically in __init__(), but frankly I wouldn't bother unless a global is out of the question due to multi-threading or whatever.

Caveat: If your process is in the middle of a system call, handling an signal may interrupt the system call. So this may not be safe for all applications. Safer alternatives would be (a) Instead of relying on signals, use a non-blocking read at the end of each loop iteration (and type input instead of hitting ^C); (b) use threads or interprocess communication to isolate the worker from the signal handling; or (c) do the work of implementing real signal blocking, if you are on an OS that has it. All of them are OS-dependent to some extent, so I'll leave it at that.

the below logic will help you do this,

import signalimport sysimport timerun = Truedef signal_handler(signal, frame):    global run    print "exiting"    run = Falsesignal.signal(signal.SIGINT, signal_handler)while run:    print "hi"    time.sleep(1)    # do anything    print "bye"

while running this, try pressing CTRL+C

I hope below code would help you:

#!/bin/pythonimport sysimport timeimport signaldef cb_sigint_handler(signum, stack):    global is_interrupted    print "SIGINT received"    is_interrupted = Trueif __name__ == "__main__":    is_interrupted = False    signal.signal(signal.SIGINT, cb_sigint_handler)    while(1):        # do stuff here         print "processing..."        time.sleep(3)        if is_interrupted:            print "Exiting.."            # do clean up            sys.exit(0)