how to read frame width of video in cv2

1import cv2
2
3vcap = cv2.VideoCapture('video.avi') # 0=camera
4 
5if vcap.isOpened(): 
6    # get vcap property 
7    width  = vcap.get(cv2.cv.CV_CAP_PROP_FRAME_WIDTH)   # float `width`
8    height = vcap.get(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT)  # float `height`
9    # or
10    width  = vcap.get(3)  # float `width`
11    height = vcap.get(4)  # float `height`
12
13    # it gives me 0.0 :/
14    fps = vcap.get(cv2.cv.CV_CAP_PROP_FPS)
15