AttributeError: module ‘cv2’ has no attribute ‘cv’ python raspberry pi

from multiprocessing import Process, Queue
import time
import cv2

# Upper limit
_Servo1UL = 250
_Servo0UL = 230

# Lower Limit
_Servo1LL = 75
_Servo0LL = 70


ServoBlaster = open('/dev/servoblaster', 'w')       # ServoBlaster is what we use to control the servo motors

webcam = cv2.VideoCapture(0)                # Get ready to start getting images from the webcam
webcam.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, 320)     # I have found this to be about the highest-
webcam.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, 240)    #   resolution you'll want to attempt on the pi

Traceback (most recent call last):
  File "/home/anisrahali/Desktop/PiFace.py", line 17, in <module>
    webcam.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, 320)     # I have found this to be about the highest-
AttributeError: module 'cv2' has no attribute 'cv'

i tried to install ‘pip install opencv-python’
what to do i need answer ASAP please