What's the simplest way of detecting keyboard input in a script from the terminal?

Question

I have a simple python script, that has some functions that run in a loop (I'm taking sensor readings).

while True:
    print "Doing a function"

If the keyboard is pressed I'd like to print "key pressed".

What's the simplest way of doing this in Python? I've searched high and low. I've found out how to do it with pygame, but I'd rather do it without. If I do have to use pygame is it possible to not have a separate window for the application?:

import pygame, time
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((640, 480))
pygame.display.set_caption('Pygame Keyboard Test')
pygame.mouse.set_visible(0)


while True:

   print "doing a function"

    for event in pygame.event.get():
      if (event.type == KEYUP) or (event.type == KEYDOWN):
         print "key pressed"
         time.sleep(0.1)

Solution 1

Edit:

I've thought about this problem a lot, and there are a few different behaviors one could want. I've been implementing most of them for Unix and Windows, and will post them here once they are done.

Synchronous/Blocking key capture:

1. A simple input or raw_input, a blocking function which returns text typed by a user once they press a newline.
2. A simple blocking function that waits for the user to press a single key, then returns that key

Asynchronous key capture:

1. A callback that is called with the pressed key whenever the user types a key into the command prompt, even when typing things into an interpreter (a keylogger)
2. A callback that is called with the typed text after the user presses enter (a less realtime keylogger)
3. A callback that is called with the keys pressed when a program is running (say, in a for loop or while loop)

Polling:

1. The user simply wants to be able to do something when a key is pressed, without having to wait for that key (so this should be non-blocking). Thus they call a poll() function and that either returns a key, or returns None. This can either be lossy (if they take too long to between poll they can miss a key) or non-lossy (the poller will store the history of all keys pressed, so when the poll() function requests them they will always be returned in the order pressed).

2. The same as 1, except that poll only returns something once the user presses a newline.

Robots:

These are something that can be called to programmatically fire keyboard events. This can be used alongside key captures to echo them back out to the user

Implementations

Synchronous/Blocking key capture:

A simple input or raw_input, a blocking function which returns text typed by a user once they press a newline.

typedString = raw_input()

A simple blocking function that waits for the user to press a single key, then returns that key

class _Getch:
    """Gets a single character from standard input.  Does not echo to the
screen. From http://code.activestate.com/recipes/134892/"""
    def __init__(self):
        try:
            self.impl = _GetchWindows()
        except ImportError:
            try:
                self.impl = _GetchMacCarbon()
            except(AttributeError, ImportError):
                self.impl = _GetchUnix()

    def __call__(self): return self.impl()


class _GetchUnix:
    def __init__(self):
        import tty, sys, termios # import termios now or else you'll get the Unix version on the Mac

    def __call__(self):
        import sys, tty, termios
        fd = sys.stdin.fileno()
        old_settings = termios.tcgetattr(fd)
        try:
            tty.setraw(sys.stdin.fileno())
            ch = sys.stdin.read(1)
        finally:
            termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
        return ch

class _GetchWindows:
    def __init__(self):
        import msvcrt

    def __call__(self):
        import msvcrt
        return msvcrt.getch()

class _GetchMacCarbon:
    """
    A function which returns the current ASCII key that is down;
    if no ASCII key is down, the null string is returned.  The
    page http://www.mactech.com/macintosh-c/chap02-1.html was
    very helpful in figuring out how to do this.
    """
    def __init__(self):
        import Carbon
        Carbon.Evt #see if it has this (in Unix, it doesn't)

    def __call__(self):
        import Carbon
        if Carbon.Evt.EventAvail(0x0008)[0]==0: # 0x0008 is the keyDownMask
            return ''
        else:
            #
            # The event contains the following info:
            # (what,msg,when,where,mod)=Carbon.Evt.GetNextEvent(0x0008)[1]
            #
            # The message (msg) contains the ASCII char which is
            # extracted with the 0x000000FF charCodeMask; this
            # number is converted to an ASCII character with chr() and
            # returned
            #
            (what,msg,when,where,mod)=Carbon.Evt.GetNextEvent(0x0008)[1]
            return chr(msg & 0x000000FF)


def getKey():
    inkey = _Getch()
    import sys
    for i in xrange(sys.maxint):
        k=inkey()
        if k<>'':break

    return k

Asynchronous key capture:

A callback that is called with the pressed key whenever the user types a key into the command prompt, even when typing things into an interpreter (a keylogger)

A callback that is called with the typed text after the user presses enter (a less realtime keylogger)

Windows:

This uses the windows Robot given below, naming the script keyPress.py

# Some if this is from http://nullege.com/codes/show/src@e@i@einstein-HEAD@Python25Einstein@[email protected]/380/win32api.GetStdHandle
# and
# http://nullege.com/codes/show/src@v@i@VistA-HEAD@Python@[email protected]/901/win32console.GetStdHandle.PeekConsoleInput

from ctypes import *
import time
import threading

from win32api import STD_INPUT_HANDLE, STD_OUTPUT_HANDLE

from win32console import GetStdHandle, KEY_EVENT, ENABLE_WINDOW_INPUT, ENABLE_MOUSE_INPUT, ENABLE_ECHO_INPUT, ENABLE_LINE_INPUT, ENABLE_PROCESSED_INPUT

import keyPress


class CaptureLines():
    def __init__(self):
        self.stopLock = threading.Lock()

        self.isCapturingInputLines = False

        self.inputLinesHookCallback = CFUNCTYPE(c_int)(self.inputLinesHook)
        self.pyosInputHookPointer = c_void_p.in_dll(pythonapi, "PyOS_InputHook")
        self.originalPyOsInputHookPointerValue = self.pyosInputHookPointer.value

        self.readHandle = GetStdHandle(STD_INPUT_HANDLE)
        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)

    def inputLinesHook(self):

        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)
        inputChars = self.readHandle.ReadConsole(10000000)
        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_PROCESSED_INPUT)

        if inputChars == "\r\n":
            keyPress.KeyPress("\n")
            return 0

        inputChars = inputChars[:-2]

        inputChars += "\n"

        for c in inputChars:
            keyPress.KeyPress(c)

        self.inputCallback(inputChars)

        return 0


    def startCapture(self, inputCallback):
        self.stopLock.acquire()

        try:
            if self.isCapturingInputLines:
                raise Exception("Already capturing keystrokes")

            self.isCapturingInputLines = True
            self.inputCallback = inputCallback

            self.pyosInputHookPointer.value = cast(self.inputLinesHookCallback, c_void_p).value
        except Exception as e:
            self.stopLock.release()
            raise

        self.stopLock.release()

    def stopCapture(self):
        self.stopLock.acquire()

        try:
            if not self.isCapturingInputLines:
                raise Exception("Keystrokes already aren't being captured")

            self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)

            self.isCapturingInputLines = False
            self.pyosInputHookPointer.value = self.originalPyOsInputHookPointerValue

        except Exception as e:
            self.stopLock.release()
            raise

        self.stopLock.release()

A callback that is called with the keys pressed when a program is running (say, in a for loop or while loop)

Windows:

import threading
from win32api import STD_INPUT_HANDLE
from win32console import GetStdHandle, KEY_EVENT, ENABLE_ECHO_INPUT, ENABLE_LINE_INPUT, ENABLE_PROCESSED_INPUT


class KeyAsyncReader():
    def __init__(self):
        self.stopLock = threading.Lock()
        self.stopped = True
        self.capturedChars = ""

        self.readHandle = GetStdHandle(STD_INPUT_HANDLE)
        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)



    def startReading(self, readCallback):
        self.stopLock.acquire()

        try:
            if not self.stopped:
                raise Exception("Capture is already going")

            self.stopped = False
            self.readCallback = readCallback

            backgroundCaptureThread = threading.Thread(target=self.backgroundThreadReading)
            backgroundCaptureThread.daemon = True
            backgroundCaptureThread.start()
        except:
            self.stopLock.release()
            raise

        self.stopLock.release()


    def backgroundThreadReading(self):
        curEventLength = 0
        curKeysLength = 0
        while True:
            eventsPeek = self.readHandle.PeekConsoleInput(10000)

            self.stopLock.acquire()
            if self.stopped:
                self.stopLock.release()
                return
            self.stopLock.release()


            if len(eventsPeek) == 0:
                continue

            if not len(eventsPeek) == curEventLength:
                if self.getCharsFromEvents(eventsPeek[curEventLength:]):
                    self.stopLock.acquire()
                    self.stopped = True
                    self.stopLock.release()
                    break

                curEventLength = len(eventsPeek)



    def getCharsFromEvents(self, eventsPeek):
        callbackReturnedTrue = False
        for curEvent in eventsPeek:
            if curEvent.EventType == KEY_EVENT:
                    if ord(curEvent.Char) == 0 or not curEvent.KeyDown:
                        pass
                    else:
                        curChar = str(curEvent.Char)
                        if self.readCallback(curChar) == True:
                            callbackReturnedTrue = True


        return callbackReturnedTrue

    def stopReading(self):
        self.stopLock.acquire()
        self.stopped = True
        self.stopLock.release()

Polling:

The user simply wants to be able to do something when a key is pressed, without having to wait for that key (so this should be non-blocking). Thus they call a poll() function and that either returns a key, or returns None. This can either be lossy (if they take too long to between poll they can miss a key) or non-lossy (the poller will store the history of all keys pressed, so when the poll() function requests them they will always be returned in the order pressed).

Windows and OS X (and maybe Linux):

global isWindows

isWindows = False
try:
    from win32api import STD_INPUT_HANDLE
    from win32console import GetStdHandle, KEY_EVENT, ENABLE_ECHO_INPUT, ENABLE_LINE_INPUT, ENABLE_PROCESSED_INPUT
    isWindows = True
except ImportError as e:
    import sys
    import select
    import termios


class KeyPoller():
    def __enter__(self):
        global isWindows
        if isWindows:
            self.readHandle = GetStdHandle(STD_INPUT_HANDLE)
            self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)

            self.curEventLength = 0
            self.curKeysLength = 0

            self.capturedChars = []
        else:
            # Save the terminal settings
            self.fd = sys.stdin.fileno()
            self.new_term = termios.tcgetattr(self.fd)
            self.old_term = termios.tcgetattr(self.fd)

            # New terminal setting unbuffered
            self.new_term[3] = (self.new_term[3] & ~termios.ICANON & ~termios.ECHO)
            termios.tcsetattr(self.fd, termios.TCSAFLUSH, self.new_term)

        return self

    def __exit__(self, type, value, traceback):
        if isWindows:
            pass
        else:
            termios.tcsetattr(self.fd, termios.TCSAFLUSH, self.old_term)

    def poll(self):
        if isWindows:
            if not len(self.capturedChars) == 0:
                return self.capturedChars.pop(0)

            eventsPeek = self.readHandle.PeekConsoleInput(10000)

            if len(eventsPeek) == 0:
                return None

            if not len(eventsPeek) == self.curEventLength:
                for curEvent in eventsPeek[self.curEventLength:]:
                    if curEvent.EventType == KEY_EVENT:
                        if ord(curEvent.Char) == 0 or not curEvent.KeyDown:
                            pass
                        else:
                            curChar = str(curEvent.Char)
                            self.capturedChars.append(curChar)
                self.curEventLength = len(eventsPeek)

            if not len(self.capturedChars) == 0:
                return self.capturedChars.pop(0)
            else:
                return None
        else:
            dr,dw,de = select.select([sys.stdin], [], [], 0)
            if not dr == []:
                return sys.stdin.read(1)
            return None

Simple use case:

with KeyPoller() as keyPoller:
    while True:
        c = keyPoller.poll()
        if not c is None:
            if c == "c":
                break
            print c

The same as above, except that poll only returns something once the user presses a newline.

Robots:

These are something that can be called to programmatically fire keyboard events. This can be used alongside key captures to echo them back out to the user

Windows:

# Modified from http://stackoverflow.com/a/13615802/2924421

import ctypes
from ctypes import wintypes
import time

user32 = ctypes.WinDLL('user32', use_last_error=True)

INPUT_MOUSE    = 0
INPUT_KEYBOARD = 1
INPUT_HARDWARE = 2

KEYEVENTF_EXTENDEDKEY = 0x0001
KEYEVENTF_KEYUP       = 0x0002
KEYEVENTF_UNICODE     = 0x0004
KEYEVENTF_SCANCODE    = 0x0008

MAPVK_VK_TO_VSC = 0

# C struct definitions
wintypes.ULONG_PTR = wintypes.WPARAM

SendInput = ctypes.windll.user32.SendInput

PUL = ctypes.POINTER(ctypes.c_ulong)

class KEYBDINPUT(ctypes.Structure):
    _fields_ = (("wVk",         wintypes.WORD),
                ("wScan",       wintypes.WORD),
                ("dwFlags",     wintypes.DWORD),
                ("time",        wintypes.DWORD),
                ("dwExtraInfo", wintypes.ULONG_PTR))

class MOUSEINPUT(ctypes.Structure):
    _fields_ = (("dx",          wintypes.LONG),
                ("dy",          wintypes.LONG),
                ("mouseData",   wintypes.DWORD),
                ("dwFlags",     wintypes.DWORD),
                ("time",        wintypes.DWORD),
                ("dwExtraInfo", wintypes.ULONG_PTR))

class HARDWAREINPUT(ctypes.Structure):
    _fields_ = (("uMsg",    wintypes.DWORD),
                ("wParamL", wintypes.WORD),
                ("wParamH", wintypes.WORD))

class INPUT(ctypes.Structure):
    class _INPUT(ctypes.Union):
        _fields_ = (("ki", KEYBDINPUT),
                    ("mi", MOUSEINPUT),
                    ("hi", HARDWAREINPUT))
    _anonymous_ = ("_input",)
    _fields_ = (("type",   wintypes.DWORD),
                ("_input", _INPUT))

LPINPUT = ctypes.POINTER(INPUT)

def _check_count(result, func, args):
    if result == 0:
        raise ctypes.WinError(ctypes.get_last_error())
    return args

user32.SendInput.errcheck = _check_count
user32.SendInput.argtypes = (wintypes.UINT, # nInputs
                             LPINPUT,       # pInputs
                             ctypes.c_int)  # cbSize

def KeyDown(unicodeKey):
    key, unikey, uniflag = GetKeyCode(unicodeKey)
    x = INPUT( type=INPUT_KEYBOARD, ki= KEYBDINPUT( key, unikey, uniflag, 0))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def KeyUp(unicodeKey):
    key, unikey, uniflag = GetKeyCode(unicodeKey)
    extra = ctypes.c_ulong(0)
    x = INPUT( type=INPUT_KEYBOARD, ki= KEYBDINPUT( key, unikey, uniflag | KEYEVENTF_KEYUP, 0))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def KeyPress(unicodeKey):
    time.sleep(0.0001)
    KeyDown(unicodeKey)
    time.sleep(0.0001)
    KeyUp(unicodeKey)
    time.sleep(0.0001)


def GetKeyCode(unicodeKey):
    k = unicodeKey
    curKeyCode = 0
    if k == "up": curKeyCode = 0x26
    elif k == "down": curKeyCode = 0x28
    elif k == "left": curKeyCode = 0x25
    elif k == "right": curKeyCode = 0x27
    elif k == "home": curKeyCode = 0x24
    elif k == "end": curKeyCode = 0x23
    elif k == "insert": curKeyCode = 0x2D
    elif k == "pgup": curKeyCode = 0x21
    elif k == "pgdn": curKeyCode = 0x22
    elif k == "delete": curKeyCode = 0x2E
    elif k == "\n": curKeyCode = 0x0D

    if curKeyCode == 0:
        return 0, int(unicodeKey.encode("hex"), 16), KEYEVENTF_UNICODE
    else:
        return curKeyCode, 0, 0

OS X:

#!/usr/bin/env python

import time
from Quartz.CoreGraphics import CGEventCreateKeyboardEvent
from Quartz.CoreGraphics import CGEventPost

# Python releases things automatically, using CFRelease will result in a scary error
#from Quartz.CoreGraphics import CFRelease

from Quartz.CoreGraphics import kCGHIDEventTap

# From http://stackoverflow.com/questions/281133/controlling-the-mouse-from-python-in-os-x
# and from https://developer.apple.com/library/mac/documentation/Carbon/Reference/QuartzEventServicesRef/index.html#//apple_ref/c/func/CGEventCreateKeyboardEvent


def KeyDown(k):
    keyCode, shiftKey = toKeyCode(k)

    time.sleep(0.0001)

    if shiftKey:
        CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, 0x38, True))
        time.sleep(0.0001)

    CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, keyCode, True))
    time.sleep(0.0001)

    if shiftKey:
        CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, 0x38, False))
        time.sleep(0.0001)

def KeyUp(k):
    keyCode, shiftKey = toKeyCode(k)

    time.sleep(0.0001)

    CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, keyCode, False))
    time.sleep(0.0001)

def KeyPress(k):
    keyCode, shiftKey = toKeyCode(k)

    time.sleep(0.0001)

    if shiftKey:
        CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, 0x38, True))
        time.sleep(0.0001)

    CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, keyCode, True))
    time.sleep(0.0001)

    CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, keyCode, False))
    time.sleep(0.0001)

    if shiftKey:
        CGEventPost(kCGHIDEventTap, CGEventCreateKeyboardEvent(None, 0x38, False))
        time.sleep(0.0001)



# From http://stackoverflow.com/questions/3202629/where-can-i-find-a-list-of-mac-virtual-key-codes

def toKeyCode(c):
    shiftKey = False
    # Letter
    if c.isalpha():
        if not c.islower():
            shiftKey = True
            c = c.lower()

    if c in shiftChars:
        shiftKey = True
        c = shiftChars[c]
    if c in keyCodeMap:
        keyCode = keyCodeMap[c]
    else:
        keyCode = ord(c)
    return keyCode, shiftKey

shiftChars = {
    '~': '`',
    '!': '1',
    '@': '2',
    '#': '3',
    '$': '4',
    '%': '5',
    '^': '6',
    '&': '7',
    '*': '8',
    '(': '9',
    ')': '0',
    '_': '-',
    '+': '=',
    '{': '[',
    '}': ']',
    '|': '\\',
    ':': ';',
    '"': '\'',
    '<': ',',
    '>': '.',
    '?': '/'
}


keyCodeMap = {
    'a'                 : 0x00,
    's'                 : 0x01,
    'd'                 : 0x02,
    'f'                 : 0x03,
    'h'                 : 0x04,
    'g'                 : 0x05,
    'z'                 : 0x06,
    'x'                 : 0x07,
    'c'                 : 0x08,
    'v'                 : 0x09,
    'b'                 : 0x0B,
    'q'                 : 0x0C,
    'w'                 : 0x0D,
    'e'                 : 0x0E,
    'r'                 : 0x0F,
    'y'                 : 0x10,
    't'                 : 0x11,
    '1'                 : 0x12,
    '2'                 : 0x13,
    '3'                 : 0x14,
    '4'                 : 0x15,
    '6'                 : 0x16,
    '5'                 : 0x17,
    '='                 : 0x18,
    '9'                 : 0x19,
    '7'                 : 0x1A,
    '-'                 : 0x1B,
    '8'                 : 0x1C,
    '0'                 : 0x1D,
    ']'                 : 0x1E,
    'o'                 : 0x1F,
    'u'                 : 0x20,
    '['                 : 0x21,
    'i'                 : 0x22,
    'p'                 : 0x23,
    'l'                 : 0x25,
    'j'                 : 0x26,
    '\''                : 0x27,
    'k'                 : 0x28,
    ';'                 : 0x29,
    '\\'                : 0x2A,
    ','                 : 0x2B,
    '/'                 : 0x2C,
    'n'                 : 0x2D,
    'm'                 : 0x2E,
    '.'                 : 0x2F,
    '`'                 : 0x32,
    'k.'                : 0x41,
    'k*'                : 0x43,
    'k+'                : 0x45,
    'kclear'            : 0x47,
    'k/'                : 0x4B,
    'k\n'               : 0x4C,
    'k-'                : 0x4E,
    'k='                : 0x51,
    'k0'                : 0x52,
    'k1'                : 0x53,
    'k2'                : 0x54,
    'k3'                : 0x55,
    'k4'                : 0x56,
    'k5'                : 0x57,
    'k6'                : 0x58,
    'k7'                : 0x59,
    'k8'                : 0x5B,
    'k9'                : 0x5C,

    # keycodes for keys that are independent of keyboard layout
    '\n'                : 0x24,
    '\t'                : 0x30,
    ' '                 : 0x31,
    'del'               : 0x33,
    'delete'            : 0x33,
    'esc'               : 0x35,
    'escape'            : 0x35,
    'cmd'               : 0x37,
    'command'           : 0x37,
    'shift'             : 0x38,
    'caps lock'         : 0x39,
    'option'            : 0x3A,
    'ctrl'              : 0x3B,
    'control'           : 0x3B,
    'right shift'       : 0x3C,
    'rshift'            : 0x3C,
    'right option'      : 0x3D,
    'roption'           : 0x3D,
    'right control'     : 0x3E,
    'rcontrol'          : 0x3E,
    'fun'               : 0x3F,
    'function'          : 0x3F,
    'f17'               : 0x40,
    'volume up'         : 0x48,
    'volume down'       : 0x49,
    'mute'              : 0x4A,
    'f18'               : 0x4F,
    'f19'               : 0x50,
    'f20'               : 0x5A,
    'f5'                : 0x60,
    'f6'                : 0x61,
    'f7'                : 0x62,
    'f3'                : 0x63,
    'f8'                : 0x64,
    'f9'                : 0x65,
    'f11'               : 0x67,
    'f13'               : 0x69,
    'f16'               : 0x6A,
    'f14'               : 0x6B,
    'f10'               : 0x6D,
    'f12'               : 0x6F,
    'f15'               : 0x71,
    'help'              : 0x72,
    'home'              : 0x73,
    'pgup'              : 0x74,
    'page up'           : 0x74,
    'forward delete'    : 0x75,
    'f4'                : 0x76,
    'end'               : 0x77,
    'f2'                : 0x78,
    'page down'         : 0x79,
    'pgdn'              : 0x79,
    'f1'                : 0x7A,
    'left'              : 0x7B,
    'right'             : 0x7C,
    'down'              : 0x7D,
    'up'                : 0x7E
}

Solution 2

The Python Documentation provides this snippet to get single characters from the keyboard:

import termios, fcntl, sys, os
fd = sys.stdin.fileno()

oldterm = termios.tcgetattr(fd)
newattr = termios.tcgetattr(fd)
newattr[3] = newattr[3] & ~termios.ICANON & ~termios.ECHO
termios.tcsetattr(fd, termios.TCSANOW, newattr)

oldflags = fcntl.fcntl(fd, fcntl.F_GETFL)
fcntl.fcntl(fd, fcntl.F_SETFL, oldflags | os.O_NONBLOCK)

try:
    while 1:
        try:
            c = sys.stdin.read(1)
            if c:
                print("Got character", repr(c))
        except IOError: pass
finally:
    termios.tcsetattr(fd, termios.TCSAFLUSH, oldterm)
    fcntl.fcntl(fd, fcntl.F_SETFL, oldflags)

You can also use the PyHook module to get your job done.

Solution 3

One of the simplest way I found is to use pynput module.can be found here with nice examples as well

from pynput import keyboard

def on_press(key):
    try:
        print('alphanumeric key {0} pressed'.format(
            key.char))
    except AttributeError:
        print('special key {0} pressed'.format(
            key))

def on_release(key):
    print('{0} released'.format(
        key))
    if key == keyboard.Key.esc:
        # Stop listener
        return False

# Collect events until released
with keyboard.Listener(
        on_press=on_press,
        on_release=on_release) as listener:
    listener.join()

above is the example worked out for me and to install, go
for python 2:

    pip install pynput

for python 3:

    pip3 install pynput

Solution 4

You can use methods from http://docs.python.org/2/library/msvcrt.html if you are on Windows.

import msvcrt
....
while True:
    print "Doing a function"
    if msvcrt.kbhit():
        print "Key pressed: %s" % msvcrt.getch()

Solution 5

This worked for me on macOS Sierra and Python 2.7.10 and 3.6.3

import sys,tty,os,termios
def getkey():
    old_settings = termios.tcgetattr(sys.stdin)
    tty.setcbreak(sys.stdin.fileno())
    try:
        while True:
            b = os.read(sys.stdin.fileno(), 3).decode()
            if len(b) == 3:
                k = ord(b[2])
            else:
                k = ord(b)
            key_mapping = {
                127: 'backspace',
                10: 'return',
                32: 'space',
                9: 'tab',
                27: 'esc',
                65: 'up',
                66: 'down',
                67: 'right',
                68: 'left'
            }
            return key_mapping.get(k, chr(k))
    finally:
        termios.tcsetattr(sys.stdin, termios.TCSADRAIN, old_settings)
try:
    while True:
        k = getkey()
        if k == 'esc':
            quit()
        else:
            print(k)
except (KeyboardInterrupt, SystemExit):
    os.system('stty sane')
    print('stopping.')

View more solutions

Comments

[Tim]

Mind explaining all the extra code? (oldterm, newattr, termios, oldflags, fcntl)

[Tom R]

I'm on a mac unfortunately, but would have been nice and clean.

[Elliot A.]

Best and most helpful answer ever! If I could upvote twice I would.

[Elliot A.]

Just one thing, the getAsync messes with prints, it makes them indented(in Python3)

[Tom Swirly]

This is brilliant - I have a solution that worked for Mac OS/X but didn't shut down properly without fiddling. Have you considered releasing it as a tiny open source project?

[Phylliida]

Thanks guys =) @TomSwirly, if you think that is useful I could, I wasn't planning on it but if enough people want it I'd be happy to throw it up on github or something. However there is one major bug that I am running into that I would like to address first, I posted the question here if any of you would like to help.

[Tom Swirly]

Well, I actually didn't get it working (on OS/X) so that's all the more reason to put it up as github and figure out the details! :-) I upvoted your question but don't have a windows machine...

[Phylliida]

Okay, I have updated this so it works very well on Windows (and never actually captures the keys themselves so you never get locked up!) @TomSwirly I'll start working on the OS X version now.

[Phylliida]

If anyone is interested I created a slight variation on the original script that, in windows, calls a function every time a user types a command into the prompt (but still has the command carry though as if they just typed it). You can find it here

[drolex]

This method is blocking.

[Nathan Kovner]

kbhit() is non-blocking. getch() is only blocking if kbhit() is false, which is not possible here.

[Admin]

This is the best answer I found for creating a truly non-blocking way to get keyboard input (with mods to the while structure). I've been beating my head for days to get a way to distinguish a plain ESC from escape characters (that are prefixed with an ESC). I was able to use this for my solution.

[Oliver]

I can confirm that the polling example works on Ubuntu GNU/Linux.

[Tino Caer]

Awesome answer! Didn't have to use modules or worry about cross compatibility! raw_input works well!

[neoDev]

in python 2.7 and python 3 space is not working, and in python 3 esc gives an error: TypeError: ord() expected a character, but string of length 0 found

[bm842]

@neoDev space is not working?, what do you observe ?. I did not test with python 3 (only python 2.7), I think I should have mentioned it.

[neoDev]

have a look to the answer I posted, it works with Python 2 and 3

[bm842]

You mean you expect "space" string instead of " " (space char) when space key is pressed?

[Phylliida]

I was thinking you might actually be able to use the trace module to get the key presses directly from pyreadline or equivalents. This would let you test for and get key strokes without actually capturing them at all. Unfortunately this is dependent on interpreter/os/shell and way you are running python (if not interpreter), so it would probably have a lot of edge cases that would need a little more robust care but in theory I think it is the best option if anyone is interested in making that

[Javier Larios]

this is based on X system: File "/usr/local/lib/python3.7/dist-packages/Xlib/support/unix_co‌​nnect.py", line 76, in get_display raise error.DisplayNameEr

[madladzen]

Wouldn't recommend this actually. This is blocking code

[Luiey]

yeah, how do I integrate this script with my current script to use this listener and to run my other asyncio.get_event_loop() function?

[Rebecca Bibye]

Very helpful actually. Thank you!

[mountrix]

I have this error on Mac OS 11 : (25, 'Inappropriate ioctl for device')