fourcc = cv2.cv.FOURCC(*'XVID') AttributeError: module 'cv2' has no attribute 'cv' FOURCC

python+opencv读取视频，调用摄像头碰到了一个代码错误，如下：

python文件：

import cv2
import numpy as np

cap = cv2.VideoCapture(0)

# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi', fourcc, 20, (640, 480))

while(1):
	# get a frame
	ret, frame = cap.read()
	# save a frame
	out.write(frame)
	# show a frame
	cv2.imshow("capture", frame)
	if cv2.waitKey(1) & 0xFF == ord('q'):
		break
cap.release()
out.release()
cv2.destroyAllWindows()

Traceback (most recent call last):
  File "video_demo.py", line 31, in
    fourcc = cv2.cv.FOURCC(*'XVID')
AttributeError: 'module' object has no attribute 'cv'

这是因为我使用的是opencv 3而运行的代码是opencv2 版本的，所以代码换成opencv 3 版本就行了：
fourcc = cv2.VideoWriter_fourcc(*'XVID') 
参考：https://blog.csdn.net/w5688414/article/details/78366174