Question

I only have the python 2.6. Can I do this without using external libraries? I just want to perform a left click wherever the cursor currently is.

Answer 1

OK, first you have to know how to open the user32 windll via ctypes, which is trivial:

from ctypes import *
user32 = windll.user32

Next, the Win32 function you want to call is probably SendInput, although you might want to look at mouse_event and possibly SendMessage (and the documentation for which WM_* messages correspond to a mouse click) to compare and contrast.

Assuming you go with SendInput, you’re going to send one MOUSEEVENTF_LEFTDOWN followed by one MOUSEEVENTF_LEFTUP, with 0 for all of the params besides dwFlags.

So, how do you call this? Well, here’s the C API:

UINT WINAPI SendInput(
  _In_  UINT nInputs,
  _In_  LPINPUT pInputs,
  _In_  int cbSize
);

That LPINPUT means you’ve got a pointer to an array of INPUT structures. Since the INPUT structure itself has a union of MOUSEINPUT, KBDINPUT, and HARDWAREINPUT, you’ll also need to define those (although you can get away with just defining the first and pretending the others don’t exist, since the first is the only one you need).

So, the steps to doing this with ctypes are:

• Define the Structures for MOUSEINPUT and INPUT.
• Load the user32 windll.
• Set the argtypes for user32.SendInput.
• Create your first MOUSEINPUT instance, with dwFlags= MOUSEEVENTF_LEFTDOWN, and the INPUT instance to go with it.
• Call user32.SendInput(1, [myinput], len(INPUT)) or user32.SendInput(1, addressof(myinput), len(INPUT)) or whatever (depending on how you defined the argtypes).
• Create your second MOUSEINPUT instance, with dwFlags= MOUSEEVENTF_LEFT, and the INPUT instance to go with it.
• Call user32.SendInput() again.

One last note: On Vista and above, you have to have the right “integrity level” to do this. For example, a normal app cannot send a click to an “elevated” app (e.g., an installer). Hopefully this isn’t an issue for you. If it is, you need to read up on UIPI and UAC… and if worst comes to worst, you may need to fall back to lower-level tricks.

Is that enough, or do you need help with some specific part of this?