Simulate Keystroke in Linux With Python

Simulate keystroke in Linux with Python

Although it's specific to X, you can install the xautomation package (apt-get install xautomation on Debian-based systems) and use xte to simulate keypresses, e.g.:

from subprocess import Popen, PIPE

control_f4_sequence = '''keydown Control_L
key F4
keyup Control_L
'''

shift_a_sequence = '''keydown Shift_L
key A
keyup Shift_L
'''

def keypress(sequence):
    p = Popen(['xte'], stdin=PIPE)
    p.communicate(input=sequence)

keypress(shift_a_sequence)
keypress(control_f4_sequence)

Simulating Key Press event using Python for Linux

If the "model" is running graphically (with the X window system), the already-suggested xsendkey is a possibility, or xsendkeycode. If it's running textually (in a terminal window), then pexpect.

How to generate keyboard events?

It can be done using ctypes:

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

# msdn.microsoft.com/en-us/library/dd375731
VK_TAB  = 0x09
VK_MENU = 0x12

# C struct definitions

wintypes.ULONG_PTR = wintypes.WPARAM

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

    def __init__(self, *args, **kwds):
        super(KEYBDINPUT, self).__init__(*args, **kwds)
        # some programs use the scan code even if KEYEVENTF_SCANCODE
        # isn't set in dwFflags, so attempt to map the correct code.
        if not self.dwFlags & KEYEVENTF_UNICODE:
            self.wScan = user32.MapVirtualKeyExW(self.wVk,
                                                 MAPVK_VK_TO_VSC, 0)

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

# Functions

def PressKey(hexKeyCode):
    x = INPUT(type=INPUT_KEYBOARD,
              ki=KEYBDINPUT(wVk=hexKeyCode))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def ReleaseKey(hexKeyCode):
    x = INPUT(type=INPUT_KEYBOARD,
              ki=KEYBDINPUT(wVk=hexKeyCode,
                            dwFlags=KEYEVENTF_KEYUP))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def AltTab():
    """Press Alt+Tab and hold Alt key for 2 seconds
    in order to see the overlay.
    """
    PressKey(VK_MENU)   # Alt
    PressKey(VK_TAB)    # Tab
    ReleaseKey(VK_TAB)  # Tab~
    time.sleep(2)
    ReleaseKey(VK_MENU) # Alt~

if __name__ == "__main__":
    AltTab()

hexKeyCode is the virtual keyboard mapping as defined by the Windows API. The list of codes is available on MSDN: Virtual-Key Codes (Windows)

Simulate keyboard input linux

To insert input events into the Linux input subsystem, use the user-mode input device driver, uinput. This might help: http://thiemonge.org/getting-started-with-uinput (Note that while the tutorial references /dev/input/uinput, the correct file on my Ubuntu 12.04 PC is /dev/uinput.

How to pass a keystroke (ALT+TAB) using Popen.communicate (on Linux)?

You probably can't do exactly what your question says - pass keystrokes using Popen. You can send bytes to the stdin of the process you've opened, but it's almost certainly not looking there for them. Keyboard events are different from data coming on stdin.

The pyautogui library library could be useful for this purpose, however. Once it's installed, you could launch your viewer with Popen, as you've done, and then use

pyautogui.hotkey('alt', 'tab')

To send alt+tab to the foreground application. You may need to add a short delay to make sure ristretto has finished launching before sending the keys. See pyautogui's keyboard documentation for more details about how to use it.

How can I send keystrokes and mouse movement to a specific PID?

With ahk you can do this with Python+AutoHotkey

pip install ahk
pip install "ahk[binary]"

from ahk import AHK
from ahk.window import Window
ahk = AHK()
win = Window.from_pid(ahk, pid='20366')
win.send('abc') # send keys directly to the window

Note that some programs may simply ignore inputs when they are not in focus. However, you can test this works in general even when not in focus by testing with a program like notepad

Full disclosure: I author the ahk library.

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