Cannot install opencv-contrib-python

[christofschroeter]

Expected behaviour

I am trying to use the aruco module from OpenCV.
Got a requirements.txt from a partner which includes both opencv-contrib-python and opencv-python. Installing that using pip install -r requirements.txt did not work.

Then I followed the documentation, uninstalled both opencv-python and opencv-contrib-python and reinstalled only opencv-contrib-python.

Actual behaviour

No extra modules are provided by opencv-contrib-python. Whether I install opencv-python or opencv-contrib-python, the content of site-packages/cv2 is exactly the same.

import cv2 succeeds
from cv2 import aruco fails

I tested this on 2 computers with Linux Mint 18 and Mint 19.2 respectively. I also tried versions 3.4.3.18 (required version) and the latest version (by not requiring a specific version, resulting in 4.1.0.25). Same result.

Steps to reproduce

pip install -r requirements.txt
where requirements.txt contains:
opencv-contrib-python==3.4.3.18
opencv-python==3.4.3.18

pip uninstall opencv-python
pip uninstall opencv-contrib-python

pip install opencv-contrib-python

(I am not even sure if the previous install and uninstall makes any difference, but that is what I did).

[skvark]

where requirements.txt contains:
opencv-contrib-python==3.4.3.18
opencv-python==3.4.3.18

This is wrong. Only one of the packages gets installed (depends on the order, last one overwrites the one which was installed first) and you'll end up with a mess. You should report an issue to the project that you are using.

Additionally, if someone else is having this problem, the correct import is import cv2.aruco as aruco.