Find the different lines between two files | 接受两个参数，第一个是大文件，第二个是小文件，将小文件没有的行输出到 diff.txt 文件中

diff.py

#!/usr/bin/env python
#-*- coding: utf-8 -*-
import sys

def file_to_list(file):
    with open(file) as f:
        content = f.readlines()
    return content

if __name__ == '__main__':
    if len(sys.argv) == 3:
        pass
    else:
        print '''
Need two params:
#1 big file's name
#2 small file's name
'''
        sys.exit(-1)
    _, big_file, small_file = sys.argv
    big_content_list = file_to_list(big_file)
    small_content_list = file_to_list(small_file)

    for item in big_content_list:
        if item in small_content_list:
            pass
        else:
            with open('diff.txt', 'a') as diff:
                diff.write(item)