Python OpenCV import error with python 3.5

Question

I am having some difficulties installing opencv with python 3.5.

I have linked the cv files, but upon import cv2 I get an error saying ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/cv2.so, 2): Symbol not found: _PyCObject_Type or more specifically:

/Library/Frameworks/Python.framework/Versions/3.5/bin/python3.5 /Users/Jamie/Desktop/tester/test.py Traceback (most recent call last): File "/Users/Jamie/Desktop/tester/test.py", line 2, in import cv File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/cv.py", line 1, in from cv2.cv import * ImportError:dlopen(/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/cv2.so, 2): Symbol not found: _PyCObject_Type Referenced from: /Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/cv2.so Expected in: flat namespace in /Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/cv2.so

I have linked cv.py and cv2.so from location /usr/local/Cellar/opencv/2.4.12_2/lib/python2.7/site-packages correctly into /Library/Frameworks/Python.framework/Versions/3.5/bin

Would anybody be able to help please?

Thanks very much

Are you trying to load an opencv compiled for Python 2 using Python 3.5 ? It won't work. I documented here how I compiled opencv3 for Python 3 a few month ago, if it helps: github.com/julienpalard/grid-finder — Julien Palard
– Julien Palard, Commented May 31, 2016 at 22:26

aman · Accepted Answer · 2017-04-04 18:23:59Z

6

No need to change the python version, you can just use the pip command open cmd ( admin mode) and type

pip install opencv-python

answered Apr 4, 2017 at 18:23

aman

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JamieS · Accepted Answer · 2016-06-01 10:22:08Z

2

Found an answer - follow the instructions on this website BUT you have to change to the version of python you are using.

Also, I didn't bother with the virtual environments.

And lastly cv2.so is actually called cv2.cpython-35m-darwin.so in the build/lib folder that you make.

Then it works.

answered Jun 1, 2016 at 10:22

JamieS

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3 Comments

gglasses Over a year ago

For the future, you could also just create a symlink with ln -s cv2.cpython-35m-darwin.so cv2.so so you can import it using import cv2. :-)

Tam Over a year ago

Hey gglasses, how do I create a symlink as you said?

user391339 Over a year ago

ln -s cv2.cpython-35m-darwin.so cv2.so

stephanve · Accepted Answer · 2016-10-30 13:44:26Z

Great answer JamieS, I also followed that website. I tried to make the whole process repeatable with these make targets..

opencv-build:
    source $(VENV_DIR)/bin/activate && \
    cd $(OPENCV_SRC) && \
    mkdir -p build && \
    cd build && \
    cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=$(realpath $(BUILD_DIR)) \
    -D PYTHON3_NUMPY_INCLUDE_DIRS=$(realpath $(VENV_DIR)/lib/python3.5/site-packages/numpy/core/include) \
    -D BUILD_opencv_python3=ON \
    -D INSTALL_C_EXAMPLES=OFF \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D OPENCV_EXTRA_MODULES_PATH=$(realpath $(OPENCV_CONTRIB_SRC)/modules) \
    -D BUILD_EXAMPLES=ON ..  && \
    make -j4 -C .

To make it appear in python3 virtual env however you need to do this then:

so-copy:
    cp $(realpath $(OPENCV_SRC)/build/lib/cv2.so) $(realpath $(VENV_DIR)/lib/python3.5/site-packages/)
    cp $(realpath $(OPENCV_SRC)/build/lib/python3/cv2.cpython-35m-darwin.so) $(realpath $(VENV_DIR)/lib/python3.5/site-packages/)

Then you can test if it works..

import cv2  # Imports without problems...

I think for osx the cv2.cpython-35m-darwin.so is the only one you need, but I just copied both.

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