how to use a live camera feed instead of a video file

Hi,
I have tried the python code with a camera by ( cap = cv2.VideoCapture(0) ) but it is not working properly, every spot is always detected as occupied and frame are shown as (Frames: 0/-1 ).

So can anyone please help me to modify this code to make it work with camera feed.

And can you please tell me how to slow down the frames processed in a sec in the video mode.