Keyboard inputs are blocked when using keyboard module in python

Question

This is a question related to one of my previous questions. Back then I was working on a project that requires keyboard inputs to manipulate the python program. And I managed to do it using keyboard module. But there was a little issue. When I use keyboard module, I cannot type in a text box of another application. Simply the keyboard is locked. Can I do the same without blocking the keyboard? This is the code for a simple program that pressing 'q' would stop a for loop.

import keyboard
import os
import threading
import time

class main_prog:
    def __init__(self):
        self.loop_running = False
        self.double_previous = False
        self.start_all_threads()

    def start_loop(self, num_to_go): 
        self.loop_running = True
        for i in range(num_to_go):
            if not self.loop_running:
                break
            print(i)
            time.sleep(1)
            if self.double_previous:
                print('Double of the previous value is {}'.format(2*i))
                self.double_previous = False
        os._exit(0)

    def start_all_threads(self):
        if not self.loop_running:
            x = int(input('How far you want the count to go: '))
            t1=threading.Thread(target=self.start_loop, args=[x])
            t2=threading.Thread(target=self.start_listening_kb)
            t1.start()
            t2.start()
            t1.join()
            t2.join()

    def start_listening_kb(self):
        while True:
            if keyboard.read_key(suppress=True) == 'q':
                self.loop_running = False
            if keyboard.read_key(suppress=True) == 'd':
                self.double_previous = True

if __name__ == '__main__':
    main_prog()

I tried the pynput module also. But it blocks the keyboard too. What I want is only when the terminal (that runs this python program) is selected, pressing 'q' and 'd' doing the things that they supposed to do. How can I achieve this?

GordonAitchJay · Accepted Answer · 2022-07-28 08:49:43Z

Use pynput.

Also, your program is not thread-safe. You have different threads that read and write self.loop_running and self.double_previous without any synchronization. I have made it thread-safe by using threading.Event.

import os
import threading
import time
import pynput

class main_prog:
    def __init__(self):
        self.loop_running = threading.Event()
        self.double_previous = threading.Event()
        self.start_all_threads()
    
    def start_loop(self, num_to_go): 
        self.loop_running.set()
        for i in range(num_to_go):
            if not self.loop_running.is_set():
                break
            print(i)
            time.sleep(1)
            if self.double_previous.is_set():
                print('Double of the previous value is {}'.format(2*i))
                self.double_previous.clear()
        
        # Stops listening to keyboard events
        #self.listener.stop() # Not needed if the process is just about to end
        os._exit(0)
    
    def start_all_threads(self):
        if not self.loop_running.is_set():
            x = int(input('How far you want the count to go: '))
            
            # Collect keyboard events in a non-blocking fashion
            self.listener = pynput.keyboard.Listener(on_press=self.on_press)
            self.listener.start()
            
            t1 = threading.Thread(target=self.start_loop, args=[x])
            t1.start()
            t1.join()
    
    def on_press(self, key):
        # print(key)
        try:
            if key.char == 'q':
                self.loop_running.clear()
            elif key.char == 'd':
                self.double_previous.set()
        except AttributeError:
            pass

if __name__ == '__main__':
    main_prog()

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