Send keys to a inactive window in Python

Question

I'm trying to press a key in another process from a Python program. I've tried the win32 api, but somehow this code does nothing:

import win32gui
import win32con
import win32api

hwnd = win32gui.FindWindow("notepad", "prueba.txt: Bloc de notas")

if(hwnd != 0):

    win32api.SendMessage(hwnd, win32con.WM_KEYDOWN, win32con.VK_RETURN, 0)
    win32api.SendMessage(hwnd, win32con.WM_KEYUP, win32con.VK_RETURN, 0)

    while(True):

        win32api.SendMessage(
            hwnd,
            win32con.WM_CHAR,
            ord('x'),
            0)
else:
    print("The window is closed")

Of course I want to do this to an inactive window. Any solution or alternatives?

Thanks

Solution

Use (but add error checking)

hwndMain = win32gui.FindWindow("notepad", "prueba.txt: Bloc de notas")
hwndEdit = win32gui.FindWindowEx( hwndMain, 0, "Edit", 0 )
win32api.PostMessage( hwndEdit,win32con.WM_CHAR, ord('x'), 0)

you should add some "sleep" calls if you want to loop posting message :-)

Comments

[Admin]

Thank you guys. What about emulators and games that do not aceppt postmessage? I've tried keybd_event but it's really slow because you must wait like 0.1 seconds.

[manuell]

I you can't or don't want to use PostMessage WM_CHAR (or WM_KEYDOWN), then you are left with SendInput. I m not aware of any "wait" needed by SendInput; See msdn.microsoft.com/en-us/library/windows/desktop/ms646310.as‌​px If the code posted worked for you, you should accept the answer. You may be able to upvote answers when you'll have more reps.

[Admin]

I think SendInput doesn't work in emulators and games :(

[manuell]

Anyway, if my code helped you to fill Notepad with 'x', you may accept the answer :-) If keybd_event works, SendInput should work as well. And if SendInput doesn't work, I am not aware of another solution.