Python&Print Time&Read Images

import cv2
from time import time
star_time = time()
k=0
s="/home/s305/Desktop/1"
d = ".jpg"
for i in range(5) :
    q = s+str(i)+d
    img = cv2.imread(q)
    # img = cv2.resize(img,(240,320),1)
    img = cv2.cvtColor(img,1)
    ret,img = cv2.threshold(img,170,255,cv2.THRESH_BINARY_INV)
    cv2.imshow("s",img)
# i = time()
# cv2.waitKey(1000)
end_time = time()

print end_time-star_time