import cv2
import numpy as np
import math
cap=cv2.VideoCapture(0)
[ WARN:0] global /tmp/pip-req-build-tk9iuyva/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index
[ WARN:0] global /tmp/pip-req-build-tk9iuyva/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index