python argparse（参数解析）模块学习（一）

class ArgumentParser(_AttributeHolder, _ActionsContainer):
    """Object for parsing command line strings into Python objects.

    Keyword Arguments:
        - prog -- The name of the program (default: sys.argv[0])
        - usage -- A usage message (default: auto-generated from arguments)
        - description -- A description of what the program does
        - epilog -- Text following the argument descriptions
        - parents -- Parsers whose arguments should be copied into this one
        - formatter_class -- HelpFormatter class for printing help messages
        - prefix_chars -- Characters that prefix optional arguments
        - fromfile_prefix_chars -- Characters that prefix files containing
            additional arguments
        - argument_default -- The default value for all arguments
        - conflict_handler -- String indicating how to handle conflicts
        - add_help -- Add a -h/-help option
    """

取自argparse-1.4.0

1、prog 程序名（默认是sys.argv[0]）

import argparse
parser = argparse.ArgumentParser()
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: argparse-3.py [-h]

optional arguments:
  -h, --help  show this help message and exit

显示程序名为：argparse-3.py

可通过设置prog改变结果

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_3")
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h]

optional arguments:
  -h, --help  show this help message and exit

可见程序名已经修改为learn_argparse_3

2、usage 程序的使用用例，默认情况下回自动生成

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_3",usage="[-h] [--help] [...] [what you want???]")
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: [-h] [--help] [...] [what you want???]

optional arguments:
  -h, --help  show this help message and exit

这里可见learn_argparse_3没有打印，故在自定义usage是要注意。

可用：

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_3",usage="%(prog)s [-h] [--help] [...] [what you want???]")
parser.add_argument('bar', nargs='+', help='bar help')
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

positional arguments:
  bar         bar help

optional arguments:
  -h, --help  show this help message and exit

3、description help参数之前显示的信息

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description="A learn program")
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

A learn program

optional arguments:
  -h, --help  show this help message and exit

description经常会被调用用了简单的描述这个程序的用途，默认在信息的前后会有换行

4、epilog 收场白，可在最后加入你想展示的信息

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description="A learn program",
                                 epilog="All for one, one for all")
arg = parser.parse_args()

结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

A learn program

optional arguments:
  -h, --help  show this help message and exit

All for one, one for all

5、parents 有时候多个解析器共享一个参数，你可以将这个参数出递给parent

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int)

parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description="A learn program",
                                 epilog="All for one, one for all",
                                 parents=[parent_parser])
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

A learn program

optional arguments:
  -h, --help       show this help message and exit
  --parent PARENT

All for one, one for all

可见--parent 共享了

6、formatter_class 打印信息格式设定

    - HelpFormatter, RawDescriptionHelpFormatter, RawTextHelpFormatter,
        ArgumentDefaultsHelpFormatter -- Formatter classes which
        may be passed as the formatter_class= argument to the
        ArgumentParser constructor. HelpFormatter is the default,
        RawDescriptionHelpFormatter and RawTextHelpFormatter tell the parser
        not to change the formatting for help text, and
        ArgumentDefaultsHelpFormatter adds information about argument defaults
        to the help.

摘自argparse-1.4.0

可见formatter_class有4个参数：HelpFormatter，RawDescriptionHelpFormatter，RawTextHelpFormatter，ArgumentDefaultsHelpFormatter

• HelpFormatter 是默认参数

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int)

parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description='''
                                 other men live ti eat, while i eat to live -- socrates
                                 love rules his kingdom without a sword -- herbert''',
                                 epilog='''
                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller''',
                                 parents=[parent_parser],
                                 formatter_class=argparse.HelpFormatter)
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

other men live ti eat, while i eat to live -- socrates love rules his kingdom
without a sword -- herbert

optional arguments:
  -h, --help       show this help message and exit
  --parent PARENT

All for one, one for all -- dumas we soon believe what we desire -- chaucer
the darkest hour is that before the dawn -- fuller

可见HelpFormatter粗暴的去除了所有的'\s' '\n'

• RawDescriptionHelpFormatter，description和epilog不做修改原样输出

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int)

parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description='''
                                 other men live ti eat, while i eat to live -- socrates
                                 love rules his kingdom without a sword -- herbert''',
                                 epilog='''
                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller''',
                                 parents=[parent_parser],
                                 formatter_class=argparse.RawDescriptionHelpFormatter)
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

                                 other men live ti eat, while i eat to live -- socrates
                                 love rules his kingdom without a sword -- herbert

optional arguments:
  -h, --help       show this help message and exit
  --parent PARENT

                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller

然源码中好像在line之间加入了个indent，不明所以，有知道的小伙伴可以指导下吗？

• RawTextHelpFormatter  会保留预定意的帮助信息中的空格

• ArgumentDefaultsHelpFormatter会在HelpFormatter的基础上打印默认值给参数（测试发现在add_argument中无help参数也不会显示default）

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int,default=[1, 2, 3, 4, 5, 6])

parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description='''
                                 other men live ti eat, while i eat to live -- socrates

                                 love rules his kingdom without a sword -- herbert''',
                                 epilog='''
                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller''',
                                 parents=[parent_parser],
                                 formatter_class=argparse.RawDescriptionHelpFormatter)
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

                                 other men live ti eat, while i eat to live -- socrates

                                 love rules his kingdom without a sword -- herbert

optional arguments:
  -h, --help       show this help message and exit
  --parent PARENT

                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller

default值并没有打印出来

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int,default=[1, 2, 3, 4, 5, 6,],help='parent')

parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description='''
                                 other men live ti eat, while i eat to live -- socrates

                                 love rules his kingdom without a sword -- herbert''',
                                 epilog='''
                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller''',
                                 parents=[parent_parser],
                                 formatter_class=argparse.ArgumentDefaultsHelpFormatter)
arg = parser.parse_args()

运行结果：

argparse-learn]# python argparse-3.py -h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

other men live ti eat, while i eat to live -- socrates love rules his kingdom
without a sword -- herbert

optional arguments:
  -h, --help       show this help message and exit
  --parent PARENT  parent (default: [1, 2, 3, 4, 5, 6])

All for one, one for all -- dumas we soon believe what we desire -- chaucer
the darkest hour is that before the dawn -- fuller

7、prefix_chars 自定义前缀，默认'-'

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int,default=[1, 2, 3, 4, 5, 6,],help='parent')

parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description='''
                                 other men live ti eat, while i eat to live -- socrates

                                 love rules his kingdom without a sword -- herbert''',
                                 epilog='''
                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller''',
                                 parents=[parent_parser],
                                 formatter_class=argparse.ArgumentDefaultsHelpFormatter,
                                 prefix_chars='=')
arg = parser.parse_args()

这是不能用“python argparse-3.py -h”，会报错

运行结果：

argparse-learn]# python argparse-3.py =h
usage: learn_argparse_3 [-h] [--help] [...] [what you want???]

other men live ti eat, while i eat to live -- socrates love rules his kingdom
without a sword -- herbert

optional arguments:
  =h, ==help       show this help message and exit
  --parent PARENT  parent (default: [1, 2, 3, 4, 5, 6])

All for one, one for all -- dumas we soon believe what we desire -- chaucer
the darkest hour is that before the dawn -- fuller

8、fromfile_prefix_chars 有时候将从文件中读取参数，如果设置fromfile_prefix_chars参数的话，解析器会将带有这个前缀的参数当作文件处理

import argparse
parser = argparse.ArgumentParser(fromfile_prefix_chars='@')
parser.add_argument('-f')
print parser.parse_args(['-f', 'foo', '@args.txt'])

9、argument_default 给所有没有默认值的参数设置默认值。

import argparse
parent_parser = argparse.ArgumentParser(add_help=False)
parent_parser.add_argument("--parent", type=int,default=[1, 2, 3, 4, 5, 6,],help='parent')
parser = argparse.ArgumentParser(prog="learn_argparse_3",
                                 usage="%(prog)s [-h] [--help] [...] [what you want???]",
                                 description='''
                                 other men live ti eat, while i eat to live -- socrates

                                 love rules his kingdom without a sword -- herbert''',
                                 epilog='''
                                 All for one, one for all --                 dumas
                                 we soon believe what we desire --           chaucer
                                 the darkest hour is that before the dawn -- fuller''',
                                 parents=[parent_parser],
                                 formatter_class=argparse.ArgumentDefaultsHelpFormatter,
                                 prefix_chars='-',
                                 fromfile_prefix_chars='$',
                                 argument_default='The default value for all arguments')
parser.add_argument('--argument_default')
print parser.parse_args()

运行结果：

Namespace(argument_default='The default value for all arguments', parent=[1, 2, 3, 4, 5, 6])

10、conflict_handler argumentparser对象不允许传入俩个相同的参数，否则会报错，通过设置conflict_handler为resolve，可以用新的参数覆盖旧的同名参数

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_4",
                                 conflict_handler='resolve')
parser.add_argument('-b','--boy',help='boy')
parser.add_argument('--boy',help='girl')
parser.print_help()

运行结果：

argparse-learn]# python argparse-4.py
usage: learn_argparse_4 [-h] [-b BOY] [--boy BOY]

optional arguments:
  -h, --help  show this help message and exit
  -b BOY      boy
  --boy BOY   girl

11、add_help默认情况下ArgumentParser对象对自动添加-h/--help选项，可设置add_help=False取消

import argparse
parser = argparse.ArgumentParser(prog="learn_argparse_4",
                                 add_help=False)
parser.add_argument('boy',help='good boy help')
parser.print_help()

运行结果：

argparse-learn]# python argparse-4.py
usage: learn_argparse_4 boy

positional arguments:
  boy  good boy help