Cannot read keyboard in a loop in Python

Question

I need a Python script to read arrow keys and react to them.

As a first test:

import keyboard
import time

while True:
 if keyboard.is_pressed("i"):
  print("up")
 if keyboard.is_pressed("k"):
  print("down")
 time.sleep(0.1)

It never prints "up" but, prints characters:

i
i
j
^[[A
^[[D
^[[C

I run the script in debian terminal:

sudo python3 test.py 

I expect up or down to show up in the terminal.

What am I missing?

Answer 1

from pynput import keyboard

def on_key_press(key):
    try:
        # Print the key that was pressed
        print(f'Key {key} pressed')
    except AttributeError:
        # Some special keys may not have a name attribute
        print(f'Special key {key} pressed')
 
def on_key_release(key):
    try:
        # Print the key that was released
        print(f'Key {key} released')
    except AttributeError:
        # Some special keys may not have a name attribute
        print(f'Special key {key} released')
 
# Create a keyboard listener
listener = keyboard.Listener(on_press=on_key_press, on_release=on_key_release)

# Start listening for keyboard events

listener.start()

# Keep the listener running

listener.join()

Answer 2

You're trying to use the keyboard library, but the library might not be capturing key events correctly. To detect arrow key presses, you can use the curses library instead.

Like this:

import curses

stdscr = curses.initscr()
curses.cbreak()
stdscr.keypad(1)

try:
    while True:
        key = stdscr.getch()
        if key == ord('i'):
            print("up")
        elif key == ord('k'):
            print("down")

finally:
    curses.endwin()

Also to run the script, you don't need to use sudo. Just execute python3 test.py.

Answer 3

Try this:

import keyboard

def on_key_event(e):
    if e.event_type == keyboard.KEY_DOWN:
        if e.name == 'i':
            print('up')
        elif e.name == 'j':
            print('down')

keyboard.on_press(on_key_event)

keyboard.wait('esc')  # exit key

keyboard.unhook_all()