Python loop waiting to detect keyboard key and high cpu usage

Question

Hi guys i'have made this python code to understand if a key is being pressed but it uses a lot of cpu.

I have tried using sleeping time , but this affects the key detection.

if __name__ == '__main__':
    a = b = 1
    x = [0] * 4
    y = [0] * 4
    Qpremuto = False
    while (True):

        i = 0

        if keyboard.is_pressed('q'):
            Qpremuto = True

            print(i)

            x[i], y[i] = pyautogui.position()
            print(pyautogui.position())
            a = 0

            break
    time.sleep(0.2) # Not good , affects key detection

there is a way not to use the cpu but a lighter way ?

Answer 1

I'm not sure what do you mean by lighter way, but if you don't want your code to "pause" you can create a thread to do the loop in the background:

import threading

def thread_function():
    while (True):
            i = 0
            if keyboard.is_pressed('q'):
                Qpremuto = True
                print(i)

                x[i], y[i] = pyautogui.position()
                print(pyautogui.position())
                a = 0
                break

In main , simply call:

thread = Thread(target = thread_function)
thread.start()

If you want the thread to stop:

thread.join()

Answer 2

If using windows, the old kbhit and getch C functions can be used from the msvcrt library.

import msvcrt
import time

print('Press q to exit...')
while True:
    if msvcrt.kbhit() and msvcrt.getch() == b'q':  # can omit the getch if 'any key'
        # ... do something here before exit
        break
    # ... do something here in every loop
    time.sleep(0.1)  # 100ms sampling -> low CPU usage
        
# Empty Keyboard Buffer        
while msvcrt.kbhit():
    msvcrt.getch()

The sleep time can be adjusted, depending if there is any task to do on every loop, and on the workload performed.