OpenCV specify environment variables inside python file wrong documentation (OPENCV_FFMPEG_READ_ATTEMPTS) about opencv HOT 7 CLOSED

Example in the documentation is wrong because it doesn't use string. However generally this approach should work:

Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ["OPENCV_FOR_THREADS_NUM"] = "3"
>>> import cv2
>>> cv2.getNumThreads()
3

Default value without environment change:

Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> cv2.getNumThreads()
4

from opencv.

Most probably the same as https://stackoverflow.com/questions/5153547/environment-variables-are-different-for-dll-than-exe. It's not related to OpenCV, but OS specific.

from opencv.

Dear @LaurentBerger,

I understood the Python Doc but I honestly don't know what to understand in your quoted paragraph. 😕

What I said is that the code provided inside the OpenCV Doc to modify os environment variable, executed as is, raises an error.

The code that reads a video frame doesn't matter much, and it's embedded through MMCV that uses OpenCV, so I'm not able to provide a OpenCV-code-only example. I know this part works, because as I said, it works once the environment variable modified inside Windows parameters.

Please tell me if you really need an example for reading a video frame but I think it's not necessary, as I guess the problem will occur on the set up of every possible OpenCV environment variable.

from opencv.

first read python doc :

I don't see anything in your code about reading a video

from opencv.

i meet with same problem

from opencv.

os.environ["MY_ENV_VARIABLE"] = True
True is not a string
and now I search in doc and I found reference:

I think you can make a PR to change python code

from opencv.

I don't understand : opencv documentation is wrong for python

there is a bug in opencv documentation because if you follow documentation it raises an execption

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