read live video from usb opencv python
import cv2
cap = cv2.VideoCapture()
# The device number might be 0 or 1 depending on the device and the webcam
cap.open(0, cv2.CAP_DSHOW)
while(True):
ret, frame = cap.read()
cv2.imshow('frame', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()