Passing a local variable outside of a function

[Gribouillis]

I don't understand the WinDLL part but you could try a callable object

def folder_exists(folder):
    enum_func = ctypes.WINFUNCTYPE(wintypes.BOOL,
                                   wintypes.HWND,
                                   wintypes.LPARAM)
    class Query:
        def __call__(self, hwnd, lParam):
            self.found = 0
            length = ctypes.WinDLL('User32').GetWindowTextLengthW(hwnd) + 1
            buf = ctypes.create_unicode_buffer(length)
            ctypes.WinDLL('User32').GetWindowTextW(hwnd, buf, length)
            if buf.value == folder:
                self.found += 1
            return True
    query = Query()
    worker = enum_func(query)
    ctypes.WinDLL('User32').EnumWindows(worker, None)
    print(query.found)
 
folder_exists('Downloads')