Pause an infinite while loop with a single keypress

I’m new to python and I have been trying to find a simple way to pause an operating while-loop, making it possible to start it again from where it was paused. I have searched on Google for help and tips, but everything I find seems very complex. Is there a simple way to do this?

I’ve read that you can use termios and tkinter.

I’m using ubuntu.

Answer

Here’s a simple tkinter program that runs in an infinite loop. Pressing space pauses/unpauses it, and pressing Esc quits.

Note: The following is for Python 2.x, if you’re using Python 3, change Tkinter in the first line to tkinter (lower case t).

from Tkinter import *
import time

class MyLoop():
    def __init__(self, root):
        self.running = True
        self.aboutToQuit = False
        self.root = root
        self.someVar = 0
        self.root.bind("<space>", self.switch)
        self.root.bind("<Escape>", self.exit) 

        while not self.aboutToQuit:
            self.root.update() # always process new events

            if self.running:
                # do stuff
                self.someVar += 1
                print(self.someVar)
                time.sleep(.1)

            else: # If paused, don't do anything
                time.sleep(.1)

    def switch(self, event):
        print(['Unpausing','Pausing'][self.running])
        self.running = not(self.running)

    def exit(self, event):
        self.aboutToQuit = True
        self.root.destroy()

if __name__ == "__main__":
    root = Tk()
    root.withdraw() # don't show the tkinter window
    MyLoop(root)
    root.mainloop()

This is a possible output, where I manually paused and unpaused the program twice before I quit.

1
2
3
4
5
6
7
Pausing
Unpausing
8
9
10
11
12
13
14
15
16
Pausing
Unpausing
17
18
19
20
21
22
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25