edge detection in python

cv.py

#!/usr/bin/env python2
from cv2 import *

cap = VideoCapture(0)
namedWindow('frame', flags=WINDOW_NORMAL)
createTrackbar('threshold', 'frame', 0, 1024, lambda x: x)

while(True):
    ret, frame = cap.read()
    x = getTrackbarPos('threshold','frame')
    imshow('frame',Canny(frame, x, x))
    if waitKey(1) & 0xFF == ord('q'): break

cap.release()
destroyAllWindows()