Python NameError: name 'ctypes' is not defined

Question

I am trying to call a function from a custom .dll file. But when I try to load my library SDK.dll, i get the following error. I am following the indications found here: Python import dll

Does anyone know what the problem is? I only found references of this problem for MAC enviroments.

>>> from ctypes import *
>>> lib = ctypes.WinDLL('C:/Develop/test/SDK.dll')

Traceback (most recent call last):
  File "<pyshell#19>", line 1, in <module>
    lib = ctypes.WinDLL('C:/Develop/test/SDK.dll')
NameError: name 'ctypes' is not defined

Piotr Hajduga · Accepted Answer · 2013-04-08 10:58:37Z

11

By doing from ctypes import * you are pulling everything from ctypes module to local namespace, so you should be calling WinDLL directly:

>>> from ctypes import *
>>> lib = WinDLL('C:/Develop/test/SDK.dll')

Another (and as mentioned by NPE usually better) way to do it is to import just ctypes:

>>> import ctypes
>>> lib = ctypes.WinDLL('C:/Develop/test/SDK.dll')

answered Apr 8, 2013 at 10:58

Piotr Hajduga

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toni Over a year ago

Thanks a lot, it worked. Now I get another error,

Traceback (most recent call last):   File "<pyshell#21>", line 1, in <module>     lib = ctypes.WinDLL('C:/Develop/test/SDKApplication/Debug/SDKCore.dll')   File "C:\Python27\lib\ctypes\__init__.py", line 365, in __init__     self._handle = _dlopen(self._name, mode) WindowsError: [Error 193] %1 is not a valid Win32 application

, but I think this might be due to the fact that my python is 32bit, and the dll 64.

NPE · Accepted Answer · 2013-04-08 10:58:33Z

5

Change

from ctypes import *

to

import ctypes

The former imports all names from ctypes into the current namespace. It is generally considered to be a bad practice and is best avoided.

answered Apr 8, 2013 at 10:58

NPE

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1 Comment

toni Over a year ago

Thanks a lot, it worked. Now I get another error,

Traceback (most recent call last):   File "<pyshell#21>", line 1, in <module>     lib = ctypes.WinDLL('C:/Develop/test/SDKApplication/Debug/SDKCore.dll')   File "C:\Python27\lib\ctypes\__init__.py", line 365, in __init__     self._handle = _dlopen(self._name, mode) WindowsError: [Error 193] %1 is not a valid Win32 application

, but I think this might be due to the fact that my python is 32bit, and the dll 64.

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