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I am trying to use an alternative version of opencv (3.0) in my Python scripts. I compiled and installed this version to my home directory, and now I am trying to tell Python to use it. I have the standard opencv version (2.4.8) installed with apt-get.

My problem is that python always imports the 2.4.8 version, even when I add the dist-packages of version 3.0 at the beginning or at the end of PYTHONPATH. Deleting opencv 2.4.8 is no option.

How could I do that correctly?

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Since OpenCV is a C library with python bindings rather than a python one, you need to tell the C environment to look in the correct library path, as well as the python one. To do that, use LD_LIBRARY_PATH. Assuming the OpenCV .so file is (say) $HOME/opencv-3.0/lib/libopencv.so.3, you do the following:

LD_LIBRARY_PATH=$HOME/opencv-3.0/lib PYTHONPATH=(...whatever...) python <script>
  • Do you know in which order the libraries are checked? /usr/lib is not part of LD_LIBRARY_PATH and so I think it is always checked before going to LD_LIBRARY_PATH, which would lead to using the older opencv version. – Mehdi Sep 15 '15 at 10:33
  • nevermind, LD_LIBRARY_PATH is checked first. – Mehdi Sep 15 '15 at 10:48

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