Python OpenCV sample subset images

sample subset images from many images

import sys,os

def fileCountIn(dir):
    return sum([len(files) for root,dirs,files in os.walk(dir)])

print "sample images:"
path = "/home/qz/Desktop/CalibGoProHero4/intrinsic/src3/"
newpath = "/home/qz/Desktop/CalibGoProHero4/intrinsic/src/"
fileCount = fileCountIn(path)
print fileCount
sample_ratio = 0.025
sample_digits = int(1/sample_ratio)
print sample_digits
index = 1
for filename in os.listdir(path):
    index = index +1
    if(index%sample_digits==0):
        print filename
        img = cv2.imread(path + filename)
        img = cv2.transpose(img)
        img = cv2.flip(img,1 )
        new_name = newpath + filename
        cv2.imwrite(new_name, img)