How to check if a button is pressed while running a program in python

Question

I want to run a program in Python while also checking the whole time whether or not a button (the physical type) has been pressed. The program looks something like this:

import stuff

a = True

def main():
        important stuff which takes about 10 seconds to complete

while True:
        if a == True:
                main() 
                #at the same time as running main(), I also want to check if a button
                #has been pressed. If so I want to set a to False

I can check if the button has been pressed after main is completed, but that would mean I would have to press the button at the split second when python checks if the button has been pressed (or hold down the button).

How can I make python check whether the button has been pressed while main() is running?

Answer 1

Here is something you can try. The main function is printing a number every second, and you can interrupt it by typing "s" + the Enter key :

import threading
import time

a = True

def main():
    for i in range(10):
        if a:
            time.sleep(1)
            print(i) 

def interrupt():
    global a # otherwise you can only read, and not modify "a" value globally
    if input("You can type 's' to stop :") == "s":
        print("interrupt !")
        a = False


t1 = threading.Thread(target=main)
t1.start()
interrupt()