在ctypes中使用dll函数 python 2.7与3.6

Question

I have a C++-Library (example.dll) with some functions and want to use them from Python. I got it working with ctypes and Python 2.7, but not with Python 3.6.

Here an excerpt from example.h :

extern "C" __declspec(dllexport) LONG _stdcall func1(LPTSTR filename, long cbAddress);

The function is parsing a txt-file, loads some data to the memory and returns a handle to this data.

My code for Python 2.7 is:

from ctypes import *

mydll = WinDLL(r'C:\temp\example.dll')
txt_path = c_char_p(r'C:\temp\file.txt')

func1 = mydll['func1']
func1.restype = c_long
func1.argtypes = (c_char_p , c_void_p)
handle = func1(txt_path, None)

This is working and returns a valid handle.

With Python 3.6, line 3 causes an error:

>>> txt_path = c_char_p(r'C:\temp\file.txt')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: bytes or integer address expected instead of str instance

so I changed it to

txt_path = c_char_p(b'C:\temp\file.txt')

which is working, but leads to a problem with the function. func1 returns now 0, which is an intern error code for "could not read txt-file."

I tried to use different types, but it didn't work and I'm kind of stuck now.

Can anyone help?

Answer 1

问题只是转义了反斜杠（有些愤世嫉俗的人可能说这是Windows），必须将有问题的行txt_path = c_char_p(b'C:\\temp\\file.txt')更改为：

txt_path = c_char_p(b'C:\\temp\\file.txt')