Question: I am following the env setup in CenterPose repo. However, opencv-python doesn't get installed. (CenterPose) mona@ada:/data/CenterPose/data$ pip install opencv-python I get this error:  -- Installing: /tmp/pip-install-wjrf6kvm/opencv-python_e5e6222fa4024d2d8f3e1d1c3bd5fb1f/_skbuild/linux-x86_64-3.6/cmake-install/share/opencv4/lbpcascades/lbpcascade_profileface.xml -- Installing: /tmp/pip-install-wjrf6kvm/opencv-python_e5e6222fa4024d2d8f3e1d1c3bd5fb1f/_skbuild/linux-x86_64-3.6/cmake-install/share/opencv4/lbpcascades/lbpcascade_silverware.xml Copying files from CMake output creating directory _skbuild/linux-x86_64-3.6/cmake-install/cv2 copying _skbuild/linux-x86_64-3.6/cmake-install/python/cv2/python-3/cv2.abi3.so -> _skbuild/linux-x86_64-3.6/cmake-install/cv2/cv2.abi3.so copying _skbuild/linux-x86_64-3.6/cmake-install/python/cv2/__init__.py -> _skbuild/linux-x86_64-3.6/cmake-install/cv2/__init__.py copying _skbuild/linux-x86_64-3.6/cmake-install/python/cv2/load_config_py2.py -> _skbuild/linux-x86_64-3.6/cmake-install/cv2/load_config_py2.py copying _skbuild/linux-x86_64-3.6/cmake-install/python/cv2/load_config_py3.py -> _skbuild/linux-x86_64-3.6/cmake-install/cv2/load_config_py3.py copying _skbuild/linux-x86_64-3.6/cmake-install/python/cv2/config.py -> _skbuild/linux-x86_64-3.6/cmake-install/cv2/config.py copying _skbuild/linux-x86_64-3.6/cmake-install/python/cv2/config-3.py -> _skbuild/linux-x86_64-3.6/cmake-install/cv2/config-3.py Traceback (most recent call last): File "/home/mona/anaconda3/envs/CenterPose/lib/python3.6/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 349, in <module> main() File "/home/mona/anaconda3/envs/CenterPose/lib/python3.6/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 331, in main json_out['return_val'] = hook(**hook_input['kwargs']) File "/home/mona/anaconda3/envs/CenterPose/lib/python3.6/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 249, in build_wheel metadata_directory) File "/tmp/pip-build-env-o9p39xto/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 231, in build_wheel wheel_directory, config_settings) File "/tmp/pip-build-env-o9p39xto/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 215, in _build_with_temp_dir self.run_setup() File "/tmp/pip-build-env-o9p39xto/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 268, in run_setup self).run_setup(setup_script=setup_script) File "/tmp/pip-build-env-o9p39xto/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 158, in run_setup exec(compile(code, __file__, 'exec'), locals()) File "setup.py", line 537, in <module> main() File "setup.py", line 310, in main cmake_source_dir=cmake_source_dir, File "/tmp/pip-build-env-o9p39xto/overlay/lib/python3.6/site-packages/skbuild/setuptools_wrap.py", line 683, in setup cmake_install_dir, File "setup.py", line 450, in _classify_installed_files_override raise Exception("Not found: '%s'" % relpath_re) Exception: Not found: 'python/cv2/py.typed' ---------------------------------------- ERROR: Failed building wheel for opencv-python Failed to build opencv-python ERROR: Could not build wheels for opencv-python which use PEP 517 and cannot be installed directly  To reproduce: CenterPose_ROOT=/path/to/clone/CenterPose git clone https://github.com/NVlabs/CenterPose.git $CenterPose_ROOT conda create -n CenterPose python=3.6 conda activate CenterPose pip install -r requirements.txt conda install -c conda-forge eigenpy  a bit sys info: (base) mona@ada:~$ uname -a Linux ada 6.5.0-21-generic #21~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Feb 9 13:32:52 UTC 2 x86_64 x86_64 x86_64 GNU/Linux (base) mona@ada:~$ lsb_release -a LSB Version: core-11.1.0ubuntu4-noarch:security-11.1.0ubuntu4-noarch Distributor ID: Ubuntu Description: Ubuntu 22.04.3 LTS Release: 22.04 Codename: jammy 

Answer: The last OpenCV version to have wheels built for Python 3.6 was v4.6. With that in mind, I was able to get everything installed by explicitly restricting to that version. Here is a standalone YAML that handles everything needed for environment creation (this doesn't require repository cloning): CenterPose_py36.yaml name: CenterPose channels: - conda-forge - nodefaults dependencies: - python=3.6 - pip - pip: - opencv-python==4.6.* - opencv-python-headless==4.6.* - -r https://github.com/NVlabs/CenterPose/raw/6c89d420b33bd01c14c13f509af08bfe3d8b2fe7/requirements.txt  I verified this works on a micromamba-docker image, simply using: micromamba create -n CenterPose -f CenterPose_py36.yaml  On conda, the command would be: conda env create -n CenterPose -f CenterPose_py36.yaml