For using external connected camera on your PC in python you can use it using

cap = cv2.VideoCapture(1)

while(1):

ret, frame = cap.read()

#print(height)

#cv2.imshow("Cropped Image", crop_img)

#gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

cv2.imshow('frame',frame)

if cv2.waitKey(1) & 0xFF == ord('q'):

break

cap.release() cv2.destroyAllWindows