Key Listeners in python?

Solution 1:

I was searching for a simple solution without window focus. Jayk's answer, pynput, works perfect for me. Here is the example how I use it.

from pynput import keyboard

def on_press(key):
    if key == keyboard.Key.esc:
        return False  # stop listener
    try:
        k = key.char  # single-char keys
    except:
        k = key.name  # other keys
    if k in ['1', '2', 'left', 'right']:  # keys of interest
        # self.keys.append(k)  # store it in global-like variable
        print('Key pressed: ' + k)
        return False  # stop listener; remove this if want more keys

listener = keyboard.Listener(on_press=on_press)
listener.start()  # start to listen on a separate thread
listener.join()  # remove if main thread is polling self.keys

Solution 2:

It's unfortunately not so easy to do that. If you're trying to make some sort of text user interface, you may want to look into curses. If you want to display things like you normally would in a terminal, but want input like that, then you'll have to work with termios, which unfortunately appears to be poorly documented in Python. Neither of these options are that simple, though, unfortunately. Additionally, they do not work under Windows; if you need them to work under Windows, you'll have to use PDCurses as a replacement for curses or pywin32 rather than termios.

I was able to get this working decently. It prints out the hexadecimal representation of keys you type. As I said in the comments of your question, arrows are tricky; I think you'll agree.

#!/usr/bin/env python
import sys
import termios
import contextlib


@contextlib.contextmanager
def raw_mode(file):
    old_attrs = termios.tcgetattr(file.fileno())
    new_attrs = old_attrs[:]
    new_attrs[3] = new_attrs[3] & ~(termios.ECHO | termios.ICANON)
    try:
        termios.tcsetattr(file.fileno(), termios.TCSADRAIN, new_attrs)
        yield
    finally:
        termios.tcsetattr(file.fileno(), termios.TCSADRAIN, old_attrs)


def main():
    print 'exit with ^C or ^D'
    with raw_mode(sys.stdin):
        try:
            while True:
                ch = sys.stdin.read(1)
                if not ch or ch == chr(4):
                    break
                print '%02x' % ord(ch),
        except (KeyboardInterrupt, EOFError):
            pass


if __name__ == '__main__':
    main()

Solution 3:

There is a way to do key listeners in python. This functionality is available through pynput.

Command line:

$ pip install pynput

Python code:

from pynput import keyboard
# your code here

Solution 4:

Here's how can do it on Windows:

"""

    Display series of numbers in infinite loop
    Listen to key "s" to stop
    Only works on Windows because listening to keys
    is platform dependent

"""

# msvcrt is a windows specific native module
import msvcrt
import time

# asks whether a key has been acquired
def kbfunc():
    #this is boolean for whether the keyboard has bene hit
    x = msvcrt.kbhit()
    if x:
        #getch acquires the character encoded in binary ASCII
        ret = msvcrt.getch()
    else:
        ret = False
    return ret

#begin the counter
number = 1

#infinite loop
while True:

    #acquire the keyboard hit if exists
    x = kbfunc() 

    #if we got a keyboard hit
    if x != False and x.decode() == 's':
        #we got the key!
        #because x is a binary, we need to decode to string
        #use the decode() which is part of the binary object
        #by default, decodes via utf8
        #concatenation auto adds a space in between
        print ("STOPPING, KEY:", x.decode())
        #break loop
        break
    else:
        #prints the number
        print (number)
        #increment, there's no ++ in python
        number += 1
        #wait half a second
        time.sleep(0.5)