使用步骤：

import 

argparse

parser=

argparse.ArgumentParser(description="test the argparse!")

parser.

add_argument('--username',default=None,help='username of Github')

parser.

parse_args()

 

1. ArgumentParser objects

class 

argparse.

ArgumentParser(

prog=None, 

usage=None, 

description=None, 

epilog=None, 

parents=[], 

formatter_class=argparse.HelpFormatter, 

prefix_chars='-', 

fromfile_prefix_chars=None, 

argument_default=None, 

conflict_handler='error', 

add_help=True, 

allow_abbrev=True)

Create a new  object. All parameters should be passed as keyword arguments. Each parameter has its own more detailed description below, but in short they are:

•  - The name of the program (default: sys.argv[0])
•  - The string describing the program usage (default: generated from arguments added to parser)
•  - Text to display before the argument help (default: none)
•  - Text to display after the argument help (default: none)
•  - A list of  objects whose arguments should also be included
•  - A class for customizing the help output
•  - The set of characters that prefix optional arguments (default: ‘-‘)
•  - The set of characters that prefix files from which additional arguments should be read (default: None)
•  - The global default value for arguments (default: None)
•  - The strategy for resolving conflicting optionals (usually unnecessary)
•  - Add a -h/--help option to the parser (default: True)
•  - Allows long options to be abbreviated if the abbreviation is unambiguous. (default: True)

Changed in version 3.5: allow_abbrev parameter was added.

 

 

2. The add_argument() method

ArgumentParser.

add_argument(

name or flags...[, 

action][, 

nargs][, 

const][, 

default][, 

type][, 

choices][, 

required][, 

help][, 

metavar][, 

dest])

Define how a single command-line argument should be parsed. Each parameter has its own more detailed description below, but in short they are:

•  - Either a name or a list of option strings, e.g. foo or -f, --foo.
•  - The basic type of action to be taken when this argument is encountered at the command line.
•  - The number of command-line arguments that should be consumed.
•  - A constant value required by some  and  selections.
•  - The value produced if the argument is absent from the command line.
•  - The type to which the command-line argument should be converted.
•  - A container of the allowable values for the argument.
•  - Whether or not the command-line option may be omitted (optionals only).
•  - A brief description of what the argument does.
•  - A name for the argument in usage messages.
•  - The name of the attribute to be added to the object returned by .

 

 

2.1. 位置参数

前面不加-或--

 

2.2. action

>>> parser.add_argument('--foo', action='store_true')注：加上--foo,那么foo=True, 不加--foo,那么foo=False>>> parser.add_argument('--foo', action='store_const', const=42)   注：加上--foo,那么foo=42, 不加--foo,那么foo=None>>> parser.add_argument('--foo', action='append')>>> parser.parse_args('--foo 1 --foo 2'.split()) Namespace(foo=['1', '2'])注：多次指定foo,把参数扩展到foo list里面

2.3. nargs

>>> parser.add_argument('--foo', nargs=2)  >>> parser.add_argument('bar', nargs=1)>>> parser.parse_args('c --foo a b'.split())Namespace(bar=['c'], foo=['a', 'b'])  注：设置nargs=1和不设置 返回的结果是不同的，nargs=2 表示后面接两个参数，并将两个参数放列表里面 >>> parser.add_argument('--foo', nargs='?', const='c', default='d')>>> parser.add_argument('bar', nargs='?', default='d')>>> parser.parse_args(['XX', '--foo', 'YY'])Namespace(bar='XX', foo='YY')>>> parser.parse_args(['XX', '--foo'])Namespace(bar='XX', foo='c')>>> parser.parse_args([])Namespace(bar='d', foo='d')注：nargs='?', const='c', default='d' 三个一起使用 意思是：脚本执行时, 若不加--foo，则foo=default的值； 若单独加--foo,则foo=const的值； 若--foo YY,则foo=YY

 

2.4. choices

>>> parser.add_argument('move', choices=['rock', 'paper', 'scissors'])>>> parser.add_argument('door', type=int, choices=range(1, 4))>>> parser.parse_args('paper 3'.split())Namespace(door=3, move='paper')注：参数的值只能从choices面选择

 

2.5. required

>>> parser.add_argument('--foo', required=True)>>> parser.parse_args(['--foo', 'BAR'])Namespace(foo='BAR')注：脚本执行时没有相应的参数会报错

  

3. The parse_args() method

ArgumentParser.

parse_args（

args = None，

namespace = None ） 将参数字符串转换为对象并将其指定为命名空间的属性。返回填充的命名空间。

 

 

4. vars 

>>> parser.add_argument('--foo')>>> args = parser.parse_args(['--foo', 'haha'])>>> parser.add_argument('--int', type=int)>>> args=parser.parse_args(['--foo','haha','--int','4'])>>> vars(args){
    'foo': 'haha', 'int': 4}注：返回的是一个字典

5. Sub-commands

>>> # create the top-level parser>>> parser = argparse.ArgumentParser(prog='PROG')>>> parser.add_argument('--foo', action='store_true', help='foo help')>>> subparsers = parser.add_subparsers(help='sub-command help')>>>>>> # create the parser for the "a" command>>> parser_a = subparsers.add_parser('a', help='a help')>>> parser_a.add_argument('bar', type=int, help='bar help')>>>>>> # create the parser for the "b" command>>> parser_b = subparsers.add_parser('b', help='b help')>>> parser_b.add_argument('--baz', choices='XYZ', help='baz help')>>>>>> # parse some argument lists>>> parser.parse_args(['a', '12'])Namespace(bar=12, foo=False)>>> parser.parse_args(['--foo', 'b', '--baz', 'Z'])Namespace(baz='Z', foo=True)