I have a situation very much like the one at ImportError: DLL load failed: %1 is not a valid Win32 application, but the answer there isn't working for me.

My Python code says:

import cv2

But that line throws the error shown in the title of this question.

I have OpenCV installed in C:\lib\opencv on this 64-bit machine. I'm using 64-bit Python.

My PYTHONPATH variable: PYTHONPATH=C:\lib\opencv\build\python\2.7. This folder contains cv2.pyd and that's all.

My PATH variable: Path=%OPENCV_DIR%\bin;... This folder contains 39 DLL files such as opencv_core246d.dll.

OPENCV_DIR has this value: OPENCV_DIR=C:\lib\opencv\build\x64\vc11.

The solution at ImportError: DLL load failed: %1 is not a valid Win32 application says to add "the new opencv binaries path (C:\opencv\build\bin\Release) to the Windows PATH environment variable". But as shown above, I already have the OpenCV binaries folder (C:\lib\opencv\build\x64\vc11\bin) in my PATH. And my OpenCV installation doesn't have any Release folders (except for an empty one under build/java).

Any ideas as to what's going wrong? Can I tell Python to verbosely trace the loading process? Exactly what DLL's is it looking for?

Thanks, Lars

EDIT:

I just noticed that, according to http://www.dependencywalker.com/, the cv2.pyd in C:\lib\opencv\build\python\2.7 is 32-bit, whereas the machine and the Python I'm running are 64-bit. Could that be the problem? And if so, where can I find a 64-bit version of cv2.pyd?

Unofficial Windows Binaries for Python Extension Packages

you can find any python libs from here

Please check if the python version you are using is also 64 bit. If not then that could be the issue. You would be using a 32 bit python version and would have installed a 64 bit binaries for the OPENCV library.

Wow, I found yet another case for this problem. None of the above worked. Eventually I used python's ability to introspect what was being loaded. For python 2.7 this means:

import imp
imp.find_module("cv2")

This turned up a completely unexpected "cv2.pyd" file in an Anaconda DLL directory that wasn't touched by multiple uninstall/install attempts. Python was looking there first and not finding my good installation. I deleted that cv2.pyd file and tried imp.find_module("cv2") again and python immediately found the right file and cv2 started working.

So if none of the other solutions work for you, make sure you use python introspection to see what file python is trying to load.

In my case, I have 64bit python, and it was lxml that was the wrong version--I should have been using the x64 version of that as well. I solved this by downloading the 64-bit version of lxml here:

https://pypi.python.org/pypi/lxml/3.4.1

lxml-3.4.1.win-amd64-py2.7.exe

This was the simplest answer to a frustrating issue.