Mean pixel of images

mean_pixel.py

#!/usr/bin/env python3
"""Start with a bang!"""

import argparse
from os import path

import cv2
import numpy as np

def main(args):
    px_acc = []
    for img_path in args.images:
        img = cv2.imread(img_path)
        px_acc.append(img.mean(1).mean(0))
    print(list(np.mean(px_acc, axis=0))[::-1])

def check_file(string):
    if not path.isfile(string):
        raise argparse.ArgumentTypeError("File {} not found".format(string))
    return string

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description="calculates the mean pixel of images")
    parser.add_argument("images", nargs="*", type=check_file)
    args = parser.parse_args()
    main(args)