Without python3.13 free-threading, cv2 importing numpy is fine. But when python3.13 free-threading is turned on, when cv2 tries to import numpy, numpy gives this error:
ImportError: Error importing numpy: you should not try to import numpy from
its source directory; please exit the numpy source tree, and relaunch
your python interpreter from there.
Does this mean cv2 and python3.13 free-threading are not compatible? I'm relatively new to cv2, python3.13 and threading :)
Starting with the 3.13 release, CPython has experimental support for a build of Python called free threading where the global interpreter lock (GIL) is disabled.
[...]
The free-threaded mode is experimental and work is ongoing to improve it: expect some bugs and a substantial single-threaded performance hit.
(From: https://docs.python.org/3/howto/free-threading-python.html. Emphasis mine.)
I think that counts as "some bugs".
You were right to try this. That's why they're offering this mode now, for users to test with all the things they care about.
You could file issues about this with the Python, OpenCV, and Numpy projects. Then they will know to investigate and work on this.
CPython (the canonical C Python implementation) tracks issues there:
https://github.com/python/cpython/issues?q=is%3Aissue%20state%3Aopen%20label%3Atopic-free-threading
It looks like pandas also has trouble importing numpy:
