What's the simplest way of detecting keyboard input in a script from the terminal?
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)
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:
- A simple
inputorraw_input, a blocking function which returns text typed by a user once they press a newline. - A simple blocking function that waits for the user to press a single key, then returns that key
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)
- A callback that is called with the keys pressed when a program is running (say, in a for loop or while loop)
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).
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
}
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.