Prints the combined MB of the files passed as arguments

combined_size.py

#!/usr/bin/env python

from __future__ import print_function
import argparse
import os

def file_size(file_name):
    """Returns size of the file named file_name in bytes."""
    if not os.path.exists(file_name):
        msg = "The file {} does not exist.".format(file_name)
        raise argparse.ArgumentTypeError(msg)
    return os.path.getsize(file_name)

def bytes_to_MB(num_bytes):
    """Returns float value"""
    return num_bytes / 1e6

def main():
    # Parse the command line arguments.
    parser = argparse.ArgumentParser(description='Prints the combined MB of ' +
                                     'the files passed as arguments.')

    parser.add_argument('file_names', nargs='*',
                        help='files that are candidates for fitting')
    parser.add_argument('--bytes', '-b', action='count',
                        help='prints the total number of bytes instead of MB')
    args = parser.parse_args()
    file_names = args.file_names
    bytes = args.bytes

    total_size = sum([file_size(fn) for fn in file_names])
    if bytes:
        print("{}".format(total_size))
    else:
        print("{}".format(bytes_to_MB(total_size)))

if __name__ == '__main__':
    main()