import argparse

# this file shows how to use argparse

# step 1，默认构造器
parser = argparse.ArgumentParser()

# step 2, 必须输入的参数，只能在1,2,4中选一个
parser.add_argument("level", type=int, choices=[1, 2, 4], help="which level to print.")

# step 3, 可选参数，默认值为4
parser.add_argument("-l" , "--len", type=float, default=4, help="length of something.")

# step 4, 转换成变量
args = parser.parse_args()
print args

# 若运行 python argparse.py -h 可查看帮助
'''
usage: argparse.py [-h] [-l LEN] {1,2,4}

positional arguments:
  {1,2,4}            which level to print.

optional arguments:
  -h, --help         show this help message and exit
  -l LEN, --len LEN  length of something.
'''

# step 5, 添加二选一的选项 --verbose | --no-verbose
feature = parse.add_mutually_exclusive_group(required=False) # 互斥组
feature.add_argument("--verbose", dest='verbose', action='store_true', help="verbose")
feature.add_argument("--no-verbose", dest='verbose', action='store_false', help='no verbose')
parser.set_defaults=(feature=True) # 默认值为True，布尔值会存在args.verbose里

# 这样子的话，输出就会多一个像这样的选项啦！ [-h] [--verbose | --no-verbose]