Stop a while loop by escape key?

Question

I edited my question because now when i ran my code outside Pycharm (IN Powershell) the keyboard interrupt works fine but now i am struggling to terminate the code on Escape key press.

from PIL import ImageGrab
import numpy as np
import cv2
import ctypes
user32 = ctypes.windll.user32
screensize = user32.GetSystemMetrics(0), user32.GetSystemMetrics(1)

def record_screen():

    fourcc = cv2.VideoWriter_fourcc(*'XVID')
    out = cv2.VideoWriter('ResultFile.avi', fourcc, 25.0, screensize)

    while True:
        try:
            img = ImageGrab.grab()
            img_np = np.array(img)
            frame = cv2.cvtColor(img_np, cv2.COLOR_BGR2RGB)
            out.write(frame)
            print('recording....')
        except KeyboardInterrupt:
            break

    out.release()
    cv2.destroyAllWindows()


record_screen()

Why not use Ctrl+C? (this would raise a `KeyboardInterrupt`) — Joel, Jul 23 '18 at 18:40
i was trying to use escape key to terminate the recording but it simply won't terminate the loop — Carl, Jul 23 '18 at 18:42
Whenever a program is running and the user presses Ctrl+C, a `KeyboardInterrupt` is raised. Try this in a Python IDE: `while True: print(1)`. Press enter, wait a few seconds, then press Ctrl+C and see what happens. — Joel, Jul 23 '18 at 18:42
after i finish recording say an excel file i go back to the IDE using ctrl+tab and press escape key but , the loop doesen't terminate — Carl, Jul 23 '18 at 18:45
https://stackoverflow.com/questions/39796689/why-doesnt-this-python-keyboard-interrupt-work-in-pycharm/39796898 — roganjosh, Jul 23 '18 at 18:48

score 0 · Answer 1 · answered Jul 23 '18 at 18:51

0

Unfortunately it's pretty difficult to listen for keypresses unless you expect one for every iteration of your loop, which for what you're doing is impractical. I think Joel has it right in the comments, you should be using

Ctrl+C

and catching the KeyboardInterrupt like this

from PIL import ImageGrab
import numpy as np
import cv2
import ctypes
user32 = ctypes.windll.user32
screensize = user32.GetSystemMetrics(0), user32.GetSystemMetrics(1)

def record_screen():

    fourcc = cv2.VideoWriter_fourcc(*'XVID')
    out = cv2.VideoWriter('ResultFile.avi', fourcc, 25.0, screensize)

    while True:
        try:
            img = ImageGrab.grab()
            img_np = np.array(img)
            frame = cv2.cvtColor(img_np, cv2.COLOR_BGR2RGB)
            out.write(frame)
            print('recording....')
        except KeyboardInterrupt:
            break

    out.release()
    cv2.destroyAllWindows()


record_screen()

This way, the KeyboardInterrupt won't terminate the program, it'll just end the while loop, allowing you to release your writer and cleanup the rest of the cv2 resources.

Because you're using PyCharm as your IDE, Ctrl+C might not work for you - try Ctrl+F2 instead.

answered Jul 23 '18 at 18:51

wpercy

9,636
4
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i tried using the above solution but the loop didn't terminate after i pressed ctrl+c – Carl Jul 23 '18 at 18:53
1

I've updated my answer for you because you use PyCharm, use ctrl+f2 – wpercy Jul 23 '18 at 18:53
i just used ctrl+f2 key but the loop still didn't terminate – Carl Jul 23 '18 at 18:54
Can't figure out the reason for this – Carl Jul 23 '18 at 18:58
and here is another problem if i use cv2.imshow('Screen', frame) just before out.write(frame) and then run my program i am able to stop the recording by pressing the escape key – Carl Jul 23 '18 at 19:00
but the downside of it is that every time the program starts the screen is bombarded with frames – Carl Jul 23 '18 at 19:01
@Carl what about this - don't put the `cv2.imshow('Screen', frame)` in the while loop, put it just before - then does it work? If you put it in the loop, it'll create a frame for each iteration, but if you put it before, it should only create one – wpercy Jul 24 '18 at 16:26

score 0 · Answer 2 · answered Jul 23 '18 at 19:04

0

You should make a variable called running! Set 'running = True' before the while loop. And instead of the while loop being 'while True:', make it 'while running = True:'. Finally, in the while loop, if you hit ESC, set 'running = False'

Here is an example with pygame:

import pygame
pygame.init()

def record():

    # init
    running = True

    while running == True:

        # record

        events = pygame.event.get()

        for event in events:

            if event.type == pygame.K_ESCAPE:

                running = False

    quit()

record()

answered Jul 23 '18 at 19:04

Terabyte

69
10

What on Earth? Where has `pygame` come from? This is not a good solution. – roganjosh Jul 23 '18 at 19:06
and it didn't helped – Carl Jul 23 '18 at 19:19
i tried the answer but the loop still ran despite pressing escape key – Carl Jul 23 '18 at 19:19

Stop a while loop by escape key?

2 Answers2