How to interrupt a program while it's running?

There are a few ways you could go about this. But pretty much you have one main issue - you need some sort of flag that can be switched such that the code will know it must stop. For instance, if the code is working in a while-loop, it should check at the start of this loop if the flag is valid, or if the flag is telling the loop to stop...

while flag: # do code 

There are a few ways to implement this flagging like operation for your needs. I will discuss the threading option. First, you need to understand how threading works, and then you need to mold your script such that instead of "running an executable" for each line of the text file, you would read the text file, and put all the lines into a queue, then you would have a few threads that read from that queue, and perform the desired action (like running an executable) but instead of running an external executable, you should mimick this with Python, this thread should be a daemon thread.. and it should have a main loop which checks if a flag that exists in the parent thread is turned on...

Below is an example:

from threading import Thread from Queue import Queue import sys import time class Performer(): def __init__(self): self.active = False self.queue = Queue() def action(self, line): pass # your code should be here def operate(self, text_file, threads=5): with open(text_file) as f: for line in f: self.queue.put(line) self.active = True thread_pool = [] for i in range(threads): t = Thread(target=self.__thread, name=('worker-%d' % i)) t.daemon = True t.start() thread_pool.append(t) while self.active: try: if self.queue.empty(): break except KeyboardInterrupt: self.active = False sys.exit('user + keyboard = byebye') else: time.sleep(1) def __thread(self): while self.active: if not self.queue.empty(): try: self.action(self.queue.get()) except Exception: pass # do something here