安装的Python模块上的ImportError

Question

I am trying to use a virtualenv to use opencv with python on OSX. I created a virtualenv with

virtualenv --system-site-packages venv

I then installed numpy and opencv with

pip install numpy opencv-python

However when I run my code using the virtualenv I get an error from the imports:

import cv2
import numpy as np

I get this error:

ImportError: No module named cv2

I haven't been able to find any information on this issue, but I can't seem to import any third party modules. It doesn't work with pandas, scipy, etc. either. Originally I was not using a virtualenv, but the other sources I found told me to try one.

Answer 1

It looks like you have installed those modules in your default/system interpreter, not into the venv you just made. You need to switch into (activate) the venv first, before installing the modules. Activate with a command something like (depending on your project's venv location):

source my_project/bin/activate

See: https://docs.python.org/3/library/venv.html

Answer 2

The following works for me:

$ virtualenv --system-site-packages venv
$ source venv/bin/activate
(venv) $ pip install numpy opencv-python
(venv) $ python
>>> import numpy as np