import ctypes, time, win32con, win32api, win32gui

PBYTE256 = ctypes.c_ubyte * 256
_user32 = ctypes.WinDLL("user32")
GetKeyboardState = _user32.GetKeyboardState
SetKeyboardState = _user32.SetKeyboardState
PostMessage = win32api.PostMessage
SendMessage = win32gui.SendMessage
FindWindow = win32gui.FindWindow
IsWindow = win32gui.IsWindow
GetCurrentThreadId = win32api.GetCurrentThreadId
GetWindowThreadProcessId = _user32.GetWindowThreadProcessId #очень важно брать функцию из dll, т.к. питоновский враппер (win32process.GetWindowThreadProcessId) выдаёт неправильные значения
AttachThreadInput = _user32.AttachThreadInput

MapVirtualKeyA = _user32.MapVirtualKeyA
MapVirtualKeyW = _user32.MapVirtualKeyW

MakeLong = win32api.MAKELONG
w = win32con #так короче запись

def PostKeyEx( hwnd, key, shift, specialkey):
    if IsWindow(hwnd):
        
        ThreadId = GetWindowThreadProcessId(hwnd, None)
        
        lparam = MakeLong(0, MapVirtualKeyA(key, 0))
        msg_down=w.WM_KEYDOWN
        msg_up=w.WM_KEYUP
        
        if specialkey:
            lparam = lparam | 0x1000000
            
        if len(shift) > 0: #Если есть модификаторы - используем PostMessage и AttachThreadInput
            pKeyBuffers = PBYTE256()
            pKeyBuffers_old = PBYTE256()
            
            SendMessage(hwnd, w.WM_ACTIVATE, w.WA_ACTIVE, 0)
            AttachThreadInput(GetCurrentThreadId(), ThreadId, True)
            GetKeyboardState( ctypes.byref(pKeyBuffers_old ))
            
            for modkey in shift:
                if modkey == w.VK_MENU:
                    lparam = lparam | 0x20000000
                    msg_down=w.WM_SYSKEYDOWN
                    msg_up=w.WM_SYSKEYUP
                pKeyBuffers[modkey] |= 128
    
            SetKeyboardState( ctypes.byref(pKeyBuffers) )
            time.sleep(0.01)
            PostMessage( hwnd, msg_down, key, lparam)
            time.sleep(0.01)
            PostMessage( hwnd, msg_up, key, lparam | 0xC0000000)
            time.sleep(0.01)
            SetKeyboardState( ctypes.byref(pKeyBuffers_old) )
            time.sleep(0.01)
            AttachThreadInput(GetCurrentThreadId(), ThreadId, False)
            
        else: #Если нету модификаторов - используем SendMessage
            SendMessage( hwnd, msg_down, key, lparam)
            SendMessage( hwnd, msg_up, key, lparam | 0xC0000000)
    
hwnd=FindWindow("Notepad", None)
PostKeyEx(hwnd,ord('A'),[w.VK_CONTROL],False)