How to save multiple images in a "for" loop?

edit

Assuming that you want to save files from a video recording, you can do this :

import cv2

vid = cv2.VideoCapture("video.mp4")
d = 0
ret, frame = vid.read()

while ret:
    ret, frame = vid.read()
    filename = "images/file_%d.jpg"%d
    cv2.imwrite(filename, frame)
    d+=1