warnings.warn('No training configuration found in save file: ' [ WARN:0] global /tmp/pip-req-build-qacpj5ci/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video1): can't open camera by index code example

Example: global /tmp/pip-req-build-civioau0/opencv/modules/videoio/src/cap_v4l.cpp (587) autosetup_capture_mode_v4l2 VIDEOIO(V4L2:/dev/video0): device is busy

Generally, you can list the available cameras with ls /dev/video* or v4l2-ctl --list-devices