ctypes 包装“MessageBoxA”示例在 python33 中不起作用

此示例位于 python 3.3.2 文档中：

http://docs.python.org/3/library/ctypes.html?highlight=ctypes#ctypes http://docs.python.org/3/library/ctypes.html?highlight=ctypes#ctypes

但是：当我在解释器中尝试时，出现错误。

我使用 Windows 7 32 python 3.3.2。

请帮忙。

from ctypes import c_int, WINFUNCTYPE, windll
from ctypes.wintypes import HWND, LPCSTR, UINT
prototype = WINFUNCTYPE(c_int, HWND, LPCSTR, LPCSTR, UINT)
paramflags = (1, "hwnd", 0), (1, "text", "Hi"), (1, "caption", None), (1, "flags", 0)
MessageBox = prototype(("MessageBoxA", windll.user32), paramflags)
MessageBox()
MessageBox(text="Spam, spam, spam")
MessageBox(flags=2, text="foo bar")

error message:
Traceback (most recent call last):
File "<string>", line 250, in run_nodebug
File "<g1>", line 7, in <module>
ctypes.ArgumentError: argument 2: <class 'TypeError'>: wrong type

猜测这是文档中的错误。 ;-)

在 Python 3 中，默认情况下所有字符串都是 Unicode，但示例是调用 ANSIMessageBoxA函数，不MessageBoxWUnicode 版本。看16.17.1.2。从加载的 dll 访问函数 http://docs.python.org/3/library/ctypes.html?highlight=ctypes#accessing-functions-from-loaded-dlls in thectypes文档。

So forMessageBoxA在示例中，您可以通过调用将函数的输入字符串参数编码为所需的内容来使其工作locale.getpreferredencoding():

from ctypes import c_int, WINFUNCTYPE, windll
from ctypes.wintypes import HWND, LPCSTR, UINT
import locale
preferred_encoding = locale.getpreferredencoding(False)
prototype = WINFUNCTYPE(c_int, HWND, LPCSTR, LPCSTR, UINT)
paramflags = ((1, "hwnd", 0), (1, "text", "Hi".encode(preferred_encoding)),
                (1, "caption", None), (1, "flags", 0))
MessageBox = prototype(("MessageBoxA", windll.user32), paramflags)

MessageBox()
MessageBox(text="Spam, spam, spam".encode(preferred_encoding))
MessageBox(flags=2, text="foo bar".encode(preferred_encoding))

使用MessageBoxW支持“宽”Unicode 字符串参数的 Windows 函数（LPCWSTR代替LPCSTR）使得几乎每次调用都不需要对它们进行显式编码。此外，我将用命名常量替换示例中的大部分“幻数”：

from ctypes import c_int, WINFUNCTYPE, windll
from ctypes.wintypes import HWND, LPCWSTR, UINT
import win32con  # contains Win32 constants pulled from the C header files
INPUT_PARM, OUTPUT_PARAM, INPUT_PARM_DEFAULT_ZERO = 1, 2, 4
prototype = WINFUNCTYPE(c_int, HWND, LPCWSTR, LPCWSTR, UINT)
paramflags = ((INPUT_PARM, "hwnd", 0),
              (INPUT_PARM, "text", "Hi"),
              (INPUT_PARM, "caption", None),
              (INPUT_PARM, "flags", win32con.MB_HELP))
MessageBox = prototype(("MessageBoxW", windll.user32), paramflags)

MessageBox()
MessageBox(text="Spam, spam, spam")
MessageBox(flags=win32con.MB_ABORTRETRYIGNORE, text="foo bar")