argparse — 命令行选项和参数解析

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2023-12-01

建立一个解析器

import argparse
parser = argparse.ArgumentParser(
    description='This is a PyMOTW sample program',
)

简单示例

# argparse_short.py
import argparse

parser = argparse.ArgumentParser(description='Short sample app')

parser.add_argument('-a', action="store_true", default=False)
parser.add_argument('-b', action="store", dest="b")
parser.add_argument('-c', action="store", dest="c", type=int)

print(parser.parse_args(['-a', '-bval', '-c', '3']))

# argparse_long.py
import argparse

parser = argparse.ArgumentParser(
    description='Example with long option names',
)

parser.add_argument('--noarg', action="store_true",
                    default=False)
parser.add_argument('--witharg', action="store",
                    dest="witharg")
parser.add_argument('--witharg2', action="store",
                    dest="witharg2", type=int)

print(
    parser.parse_args(
        ['--noarg', '--witharg', 'val', '--witharg2=3']
    )
)

# argparse_arguments.py
import argparse

parser = argparse.ArgumentParser(
    description='Example with nonoptional arguments',
)

parser.add_argument('count', action="store", type=int)
parser.add_argument('units', action="store")

print(parser.parse_args())

参数操作

# argparse_action.py
import argparse

parser = argparse.ArgumentParser()

parser.add_argument('-s', action='store',
                    dest='simple_value',
                    help='Store a simple value')

parser.add_argument('-c', action='store_const',
                    dest='constant_value',
                    const='value-to-store',
                    help='Store a constant value')

parser.add_argument('-t', action='store_true',
                    default=False,
                    dest='boolean_t',
                    help='Set a switch to true')
parser.add_argument('-f', action='store_false',
                    default=True,
                    dest='boolean_f',
                    help='Set a switch to false')

parser.add_argument('-a', action='append',
                    dest='collection',
                    default=[],
                    help='Add repeated values to a list')

parser.add_argument('-A', action='append_const',
                    dest='const_collection',
                    const='value-1-to-append',
                    default=[],
                    help='Add different values to list')
parser.add_argument('-B', action='append_const',
                    dest='const_collection',
                    const='value-2-to-append',
                    help='Add different values to list')

parser.add_argument('--version', action='version',
                    version='%(prog)s 1.0')

results = parser.parse_args()
print('simple_value     = {!r}'.format(results.simple_value))
print('constant_value   = {!r}'.format(results.constant_value))
print('boolean_t        = {!r}'.format(results.boolean_t))
print('boolean_f        = {!r}'.format(results.boolean_f))
print('collection       = {!r}'.format(results.collection))
print('const_collection = {!r}'.format(results.const_collection))

Option Prefixes

# argparse_prefix_chars.py
import argparse

parser = argparse.ArgumentParser(
    description='Change the option prefix characters',
    prefix_chars='-+/',
)

parser.add_argument('-a', action="store_false",
                    default=None,
                    help='Turn A off',
                    )
parser.add_argument('+a', action="store_true",
                    default=None,
                    help='Turn A on',
                    )
parser.add_argument('//noarg', '++noarg',
                    action="store_true",
                    default=False)

print(parser.parse_args())

Sources of Arguments

# argparse_with_shlex.py
import argparse
from configparser import ConfigParser
import shlex

parser = argparse.ArgumentParser(description='Short sample app')

parser.add_argument('-a', action="store_true", default=False)
parser.add_argument('-b', action="store", dest="b")
parser.add_argument('-c', action="store", dest="c", type=int)

config = ConfigParser()
config.read('argparse_with_shlex.ini')
config_value = config.get('cli', 'options')
print('Config  :', config_value)

argument_list = shlex.split(config_value)
print('Arg List:', argument_list)

print('Results :', parser.parse_args(argument_list))

帮助输出

# argparse_with_help.py
import argparse

parser = argparse.ArgumentParser(add_help=True)

parser.add_argument('-a', action="store_true", default=False)
parser.add_argument('-b', action="store", dest="b")
parser.add_argument('-c', action="store", dest="c", type=int)

print(parser.parse_args())

# argparse_without_help.py
import argparse

parser = argparse.ArgumentParser(add_help=False)

parser.add_argument('-a', action="store_true", default=False)
parser.add_argument('-b', action="store", dest="b")
parser.add_argument('-c', action="store", dest="c", type=int)

print(parser.parse_args())

自定义帮助

# argparse_custom_help.py
import argparse

parser = argparse.ArgumentParser(add_help=True)

parser.add_argument('-a', action="store_true", default=False)
parser.add_argument('-b', action="store", dest="b")
parser.add_argument('-c', action="store", dest="c", type=int)

print('print_usage output:')
parser.print_usage()
print()

print('print_help output:')
parser.print_help()

# argparse_raw_description_help_formatter.py
import argparse

parser = argparse.ArgumentParser(
    add_help=True,
    formatter_class=argparse.RawDescriptionHelpFormatter,
    description="""
    description
        not
           wrapped""",
    epilog="""
    epilog
      not
         wrapped""",
)

parser.add_argument(
    '-a', action="store_true",
    help="""argument
    help is
    wrapped
    """,
)

parser.print_help()

# argparse_raw_text_help_formatter.py
import argparse

parser = argparse.ArgumentParser(
    add_help=True,
    formatter_class=argparse.RawTextHelpFormatter,
    description="""
    description
        not
           wrapped""",
    epilog="""
    epilog
      not
         wrapped""",
)

parser.add_argument(
    '-a', action="store_true",
    help="""argument
    help is not
    wrapped
    """,
)

parser.print_help()

# argparse_metavar_type_help_formatter.py
import argparse

parser = argparse.ArgumentParser(
    add_help=True,
    formatter_class=argparse.MetavarTypeHelpFormatter,
)

parser.add_argument('-i', type=int, dest='notshown1')
parser.add_argument('-f', type=float, dest='notshown2')

parser.print_help()

Parser Organization

# argparse_parent_base.py
import argparse

parser = argparse.ArgumentParser(add_help=False)

parser.add_argument('--user', action="store")
parser.add_argument('--password', action="store")

# argparse_uses_parent.py
import argparse
import argparse_parent_base

parser = argparse.ArgumentParser(
    parents=[argparse_parent_base.parser],
)

parser.add_argument('--local-arg',
                    action="store_true",
                    default=False)

print(parser.parse_args())

Conflicting Options

# argparse_conflict_handler_resolve.py
import argparse

parser = argparse.ArgumentParser(conflict_handler='resolve')

parser.add_argument('-a', action="store")
parser.add_argument('-b', action="store", help='Short alone')
parser.add_argument('--long-b', '-b',
                    action="store",
                    help='Long and short together')

print(parser.parse_args(['-h']))

# argparse_conflict_handler_resolve2.py
import argparse

parser = argparse.ArgumentParser(conflict_handler='resolve')

parser.add_argument('-a', action="store")
parser.add_argument('--long-b', '-b',
                    action="store",
                    help='Long and short together')
parser.add_argument('-b', action="store", help='Short alone')

print(parser.parse_args(['-h']))

Argument Groups

# argparse_default_grouping.py
import argparse

parser = argparse.ArgumentParser(description='Short sample app')

parser.add_argument('--optional', action="store_true",
                    default=False)
parser.add_argument('positional', action="store")

print(parser.parse_args())

# argparse_parent_with_group.py
import argparse

parser = argparse.ArgumentParser(add_help=False)

group = parser.add_argument_group('authentication')

group.add_argument('--user', action="store")
group.add_argument('--password', action="store")

# argparse_uses_parent_with_group.py
import argparse
import argparse_parent_with_group

parser = argparse.ArgumentParser(
    parents=[argparse_parent_with_group.parser],
)

parser.add_argument('--local-arg',
                    action="store_true",
                    default=False)

print(parser.parse_args())

互斥选项

# argparse_mutually_exclusive.py
import argparse

parser = argparse.ArgumentParser()

group = parser.add_mutually_exclusive_group()
group.add_argument('-a', action='store_true')
group.add_argument('-b', action='store_true')

print(parser.parse_args())

Nesting Parsers

# argparse_subparsers.py
import argparse

parser = argparse.ArgumentParser()

subparsers = parser.add_subparsers(help='commands')

# A list command
list_parser = subparsers.add_parser(
    'list', help='List contents')
list_parser.add_argument(
    'dirname', action='store',
    help='Directory to list')

# A create command
create_parser = subparsers.add_parser(
    'create', help='Create a directory')
create_parser.add_argument(
    'dirname', action='store',
    help='New directory to create')
create_parser.add_argument(
    '--read-only', default=False, action='store_true',
    help='Set permissions to prevent writing to the directory',
)

# A delete command
delete_parser = subparsers.add_parser(
    'delete', help='Remove a directory')
delete_parser.add_argument(
    'dirname', action='store', help='The directory to remove')
delete_parser.add_argument(
    '--recursive', '-r', default=False, action='store_true',
    help='Remove the contents of the directory, too',
)

print(parser.parse_args())

Advanced Argument Processing

# argparse_nargs.py
import argparse

parser = argparse.ArgumentParser()

parser.add_argument('--three', nargs=3)
parser.add_argument('--optional', nargs='?')
parser.add_argument('--all', nargs='*', dest='all')
parser.add_argument('--one-or-more', nargs='+')

print(parser.parse_args())

参数类型

# argparse_type.py
import argparse

parser = argparse.ArgumentParser()

parser.add_argument('-i', type=int)
parser.add_argument('-f', type=float)
parser.add_argument('--file', type=open)

try:
    print(parser.parse_args())
except IOError as msg:
    parser.error(str(msg))

# argparse_choices.py
import argparse

parser = argparse.ArgumentParser()

parser.add_argument(
    '--mode',
    choices=('read-only', 'read-write'),
)

print(parser.parse_args())

文件参数

# argparse_FileType.py
import argparse

parser = argparse.ArgumentParser()

parser.add_argument('-i', metavar='in-file',
                    type=argparse.FileType('rt'))
parser.add_argument('-o', metavar='out-file',
                    type=argparse.FileType('wt'))

try:
    results = parser.parse_args()
    print('Input file:', results.i)
    print('Output file:', results.o)
except IOError as msg:
    parser.error(str(msg))

Custom Actions

# argparse_custom_action.py
import argparse


class CustomAction(argparse.Action):
    def __init__(self,
                 option_strings,
                 dest,
                 nargs=None,
                 const=None,
                 default=None,
                 type=None,
                 choices=None,
                 required=False,
                 help=None,
                 metavar=None):
        argparse.Action.__init__(self,
                                 option_strings=option_strings,
                                 dest=dest,
                                 nargs=nargs,
                                 const=const,
                                 default=default,
                                 type=type,
                                 choices=choices,
                                 required=required,
                                 help=help,
                                 metavar=metavar,
                                 )
        print('Initializing CustomAction')
        for name, value in sorted(locals().items()):
            if name == 'self' or value is None:
                continue
            print('  {} = {!r}'.format(name, value))
        print()
        return

    def __call__(self, parser, namespace, values,
                 option_string=None):
        print('Processing CustomAction for {}'.format(self.dest))
        print('  parser = {}'.format(id(parser)))
        print('  values = {!r}'.format(values))
        print('  option_string = {!r}'.format(option_string))

        # Do some arbitrary processing of the input values
        if isinstance(values, list):
            values = [v.upper() for v in values]
        else:
            values = values.upper()
        # Save the results in the namespace using the destination
        # variable given to our constructor.
        setattr(namespace, self.dest, values)
        print()


parser = argparse.ArgumentParser()

parser.add_argument('-a', action=CustomAction)
parser.add_argument('-m', nargs='*', action=CustomAction)

results = parser.parse_args(['-a', 'value',
                             '-m', 'multivalue',
                             'second'])
print(results)