Getting error while running a script which uses pywinauto

Question

Whenever I import pywinauto I am getting below error:

Traceback (most recent call last):
File "D:\Python\Python38\lib\ctypes_init_.py", line 123, in WINFUNCTYPE
return _win_functype_cache[(restype, argtypes, flags)]
KeyError: (<class 'ctypes.HRESULT'>, (<class 'ctypes.c_long'>, <class 'comtypes.automation.tagVARIANT'>, <class 'comtypes.LP_POINTER(IUIAutomationCondition)'>), 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:/Users/tejaw/PycharmProjects/xxxxxxxx/Sample.py", line 3, in
import pywinauto
File "D:\Python\Python38\lib\site-packages\pywinauto_init_.py", line 89, in
from . import findwindows
File "D:\Python\Python38\lib\site-packages\pywinauto\findwindows.py", line 42, in
from . import controls
File "D:\Python\Python38\lib\site-packages\pywinauto\controls_init_.py", line 36, in
from . import uiawrapper # register "uia" back-end (at the end of uiawrapper module)
File "D:\Python\Python38\lib\site-packages\pywinauto\controls\uiawrapper.py", line 47, in
from ..uia_defines import IUIA
File "D:\Python\Python38\lib\site-packages\pywinauto\uia_defines.py", line 181, in
pattern_ids = _build_pattern_ids_dic()
File "D:\Python\Python38\lib\site-packages\pywinauto\uia_defines.py", line 169, in _build_pattern_ids_dic
if hasattr(IUIA().ui_automation_client, cls_name):
File "D:\Python\Python38\lib\site-packages\pywinauto\uia_defines.py", line 50, in call
cls._instances[cls] = super(_Singleton, cls).call(*args, **kwargs)
File "D:\Python\Python38\lib\site-packages\pywinauto\uia_defines.py", line 60, in init
self.UIA_dll = comtypes.client.GetModule('UIAutomationCore.dll')
File "D:\Python\Python38\lib\site-packages\comtypes\client_generate.py", line 110, in GetModule
mod = _CreateWrapper(tlib, pathname)
File "D:\Python\Python38\lib\site-packages\comtypes\client_generate.py", line 184, in _CreateWrapper
mod = _my_import(fullname)
File "D:\Python\Python38\lib\site-packages\comtypes\client_generate.py", line 24, in my_import
return import(fullname, globals(), locals(), ['DUMMY'])
File "D:\Python\Python38\lib\site-packages\comtypes\gen_944DE083_8FB8_45CF_BCB7_C477ACB2F897_0_1_0.py", line 1931, in
IUIAutomation.methods = [
File "D:\Python\Python38\lib\site-packages\comtypes_init.py", line 329, in setattr
self.make_methods(value)
File "D:\Python\Python38\lib\site-packages\comtypes_init.py", line 698, in make_methods
prototype = WINFUNCTYPE(restype, *argtypes)
File "D:\Python\Python38\lib\ctypes_init.py", line 125, in WINFUNCTYPE
class WinFunctionType(_CFuncPtr):
TypeError: item 2 in argtypes passes a union by value, which is unsupported.

Please do help me in this.

There was a change introduced with Python 3.7.6 which created multiple issues with unions. That was reverted in 3.8.2. You can read more about it [here](https://github.com/pywinauto/pywinauto/issues/868). Could you please verify what version you're running? — Hampus Larsson, May 27 '20 at 07:32

Vasily Ryabov · Answer 1 · 2023-08-18T07:26:14.903

This is Python bug in Python 3.7.6 and 3.8.1. Please do clean install of Python 3.7.7+ or 3.8.2+.

Full history of the issue is here: https://github.com/pywinauto/pywinauto/issues/868

This is a missing feature in libffi for passing union by value. libffi is used by ctypes for resolving calling convention at runtime. Python Core developers decided to prohibit this option due to missing feature. But it was wrong decision that broke a lot of users on Windows. So the wrong patch was reverted in Python 3.7.7 / 3.8.2.

Getting error while running a script which uses pywinauto

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