python pythonnic给py增加说明

#!/usr/bin/env python
# coding=utf-8
# author: wz
# mail: 277215243@qq.com
# datetime:2018/11/6 11:33 AM
# web: https://www.bthlt.com

"""
SYNOPSIS
    ./before_days.py <days>
DESCRIPTION
    获取今天之前n天的一个列表
DEMO
    ./before_days.py 30
NOTE
   返回值包含今天，返回列表长度为输入参数 n+1
"""
import sys
import datetime


def get_before_n_days(n):
    """
    获取今天之前n天的一个列表
    """
    before_n_days = list()
    before_n_days.append(datetime.date.today().strftime('%Y%m%d'))
    for i in range(1, n)[::-1]:
        before_n_days.append((datetime.date.today() - datetime.timedelta(days=i)).strftime('%Y%m%d'))
    before_n_days.append(datetime.date.today().strftime('%Y%m%d'))
    return before_n_days


def usage():
    print sys.modules[__name__].__doc__


if __name__ == "__main__":
    if len(sys.argv) == 2:
        print sys.modules[__name__].get_before_n_days.__doc__
        days = sys.argv[1]
        days = int(days)
        print get_before_n_days(days)
    else:
        print 'Error: illegal args.'
        usage()
        exit(-1)

➜  gamerge python before_days.py 2 3
Error: illegal args.

SYNOPSIS
    ./before_days.py <days>
DESCRIPTION
    获取今天之前n天的一个列表
DEMO
    ./before_days.py 30
NOTE
   返回值包含今天，返回列表长度为输入参数 n+1

➜  gamerge python before_days.py 2

    获取今天之前n天的一个列表

['20181106', '20181105', '20181106']