快速入门
argparse是一个完整的参数处理库。参数可以根据add_argument()的action选项触发不同action。支持的action有存储参数（单个，或作为列表的一部分）;存储常量的值（对布尔开关true/false有特殊处理）。默认动作是存储参数值。支持type(指定存储类型)和dest(指定存储变量)等参数。
然后使用函数parse_args()进行参数解析，这个函数的输入默认是sys.argv[1:]，也可以使用其他字符串列表。选项使用GNU/POSIX语法处理，可以混合选项和参数值。parse_args的返回值是一个包含命令参数的Namespace。所有参数以属性的形式存在，比如args.myoption。
下面是一个简单的示例：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']))
执行结果：
$ python3 argparse_short.py
Namespace(a=True, b='val', c=3)
长参数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']
)
)
执行结果
$ python3 argparse_long.py
Namespace(noarg=True, witharg='val', witharg2=3)
混合可选和必选参数：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())
执行结果
$ python3 argparse_arguments.py 3 inches
Namespace(count=3, units='inches')
$ python3 argparse_arguments.py some inches
usage: argparse_arguments.py [-h] count units
argparse_arguments.py: error: argument count: invalid int value:
'some'
$ python3 argparse_arguments.py
usage: argparse_arguments.py [-h] count units
argparse_arguments.py: error: the following arguments are
required: count, units
参数action有：
store：默认action模式，存储值到指定变量。
store_const：存储值在参数的const部分指定，多用于实现非布尔的命令行flag。
store_true / store_false：布尔开关。可以2个参数对应一个变量。
append：存储值到列表，该参数可以重复使用。
append_const：存储值到列表，存储值在参数的const部分指定。
version 输出版本信息然后退出。
下面是各种action的示例：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))
执行结果如下，注意'simple_value'等被自动化转化为大写
$ python3 argparse_action.py -h
usage: argparse_action.py [-h] [-s SIMPLE_VALUE] [-c] [-t] [-f]
[-a COLLECTION] [-A] [-B] [--version]
optional arguments:
-h, --help show this help message and exit
-s SIMPLE_VALUE Store a simple value
-c Store a constant value
-t Set a switch to true
-f Set a switch to false
-a COLLECTION Add repeated values to a list
-A Add different values to list
-B Add different values to list
--version show program's version number and exit
$ python3 argparse_action.py -s value
simple_value = 'value'
constant_value = None
boolean_t = False
boolean_f = True
collection = []
const_collection = []
$ python3 argparse_action.py -c
simple_value = None
constant_value = 'value-to-store'
boolean_t = False
boolean_f = True
collection = []
const_collection = []
$ python3 argparse_action.py -t
simple_value = None
constant_value = None
boolean_t = True
boolean_f = True
collection = []
const_collection = []
$ python3 argparse_action.py -f
simple_value = None
constant_value = None
boolean_t = False
boolean_f = False
collection = []
const_collection = []
$ python3 argparse_action.py -a one -a two -a three
simple_value = None
constant_value = None
boolean_t = False
boolean_f = True
collection = ['one', 'two', 'three']
const_collection = []
$ python3 argparse_action.py -B -A
simple_value = None
constant_value = None
boolean_t = False
boolean_f = True
collection = []
const_collection = ['value-2-to-append', 'value-1-to-append']
$ python3 argparse_action.py --version
argparse_action.py 1.0
参考资料
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可选前缀
ArgumentParser函数中的选项prefix_chars可以指定前缀。默认使用UNIX风格，命令行使用‘-’作为前缀。可以使用windows的’/’或者其他符号。
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())
执行结果
$ python3 argparse_prefix_chars.py -h
usage: argparse_prefix_chars.py [-h] [-a] [+a] [//noarg]
Change the option prefix characters
optional arguments:
-h, --help show this help message and exit
-a Turn A off
+a Turn A on
//noarg, ++noarg
$ python3 argparse_prefix_chars.py +a
Namespace(a=True, noarg=False)
$ python3 argparse_prefix_chars.py -a
Namespace(a=False, noarg=False)
$ python3 argparse_prefix_chars.py //noarg
Namespace(a=None, noarg=True)
$ python3 argparse_prefix_chars.py ++noarg
Namespace(a=None, noarg=True)
$ python3 argparse_prefix_chars.py --noarg
usage: argparse_prefix_chars.py [-h] [-a] [+a] [//noarg]
argparse_prefix_chars.py: error: unrecognized arguments: --noarg
处理配置文件中的参数
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))
其中argparse_with_shlex.ini文件的内容如下：
[cli]
options = -a -b 2
执行结果
$ python3 argparse_with_shlex.py
Config : -a -b 2
Arg List: ['-a', '-b', '2']
Results : Namespace(a=True, b='2', c=None)
上面例子使用了ConfigParser来读取配置，再用shlex来切割参数。也可以通过fromfile_prefix_chars 告知argparse输入参数为文件。
argparse_fromfile_prefix_chars.py
import argparse
import shlex
parser = argparse.ArgumentParser(description='Short sample app',
fromfile_prefix_chars='@',
)
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_fromfile_prefix_chars.txt']))
argparse_fromfile_prefix_chars.txt
-a
-b
2
执行结果
$ python3 argparse_fromfile_prefix_chars.py
Namespace(a=True, b='2', c=None)
帮助
- 自动生成
Argparse会自动生成的帮助和版本信息。ArgumentParser的add_help参数控制帮助的生成，默认是开启。
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())
下例就关闭帮助：
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())
执行结果
$ python argparse_with_help.py -h
usage: argparse_with_help.py [-h] [-a] [-b B] [-c C]
optional arguments:
-h, --help show this help message and exit
-a
-b B
-c C
$ python argparse_without_help.py -h
usage: argparse_without_help.py [-a] [-b B] [-c C]
argparse_without_help.py: error: unrecognized arguments: -h
- 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()
执行结果
$ python3 argparse_custom_help.py
print_usage output:
usage: argparse_custom_help.py [-h] [-a] [-b B] [-c C]
print_help output:
usage: argparse_custom_help.py [-h] [-a] [-b B] [-c C]
optional arguments:
-h, --help show this help message and exit
-a
-b B
-c C
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()
执行结果
$ python3 argparse_raw_description_help_formatter.py
usage: argparse_raw_description_help_formatter.py [-h] [-a]
description
not
wrapped
optional arguments:
-h, --help show this help message and exit
-a argument help is wrapped
epilog
not
wrapped
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()
执行结果
$ python3 argparse_raw_text_help_formatter.py
usage: argparse_raw_text_help_formatter.py [-h] [-a]
description
not
wrapped
optional arguments:
-h, --help show this help message and exit
-a argument
help is not
wrapped
epilog
not
wrapped
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()
执行结果
$ python3 argparse_metavar_type_help_formatter.py
usage: argparse_metavar_type_help_formatter.py [-h] [-i int] [-f
float]
optional arguments:
-h, --help show this help message and exit
-i int
-f float
组织解析器
公共解析器:通过父子类来实现。
见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())
注意：父类关闭了help。子类却默认开启了help。执行结果：
$ python3 argparse_uses_parent.py -h
usage: argparse_uses_parent.py [-h] [--user USER]
[--password PASSWORD]
[--local-arg]
optional arguments:
-h, --help show this help message and exit
--user USER
--password PASSWORD
--local-arg
参数冲突
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']))
执行结果
$ python3 argparse_conflict_handler_resolve.py
usage: argparse_conflict_handler_resolve.py [-h] [-a A]
[--long-b LONG_B]
optional arguments:
-h, --help show this help message and exit
-a A
--long-b LONG_B, -b LONG_B
Long and short together
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']))
执行结果
$ python3 argparse_conflict_handler_resolve2.py
usage: argparse_conflict_handler_resolve2.py [-h] [-a A]
[--long-b LONG_B]
[-b B]
optional arguments:
-h, --help show this help message and exit
-a A
--long-b LONG_B Long and short together
-b B Short alone
参数分组
默认有可选参数和必选参数组。
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())
执行结果
$ python3 argparse_default_grouping.py -h
usage: argparse_default_grouping.py [-h] [--optional] positional
Short sample app
positional arguments:
positional
optional arguments:
-h, --help show this help message and exit
--optional
前面的用户名和密码就可以分组：
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())
执行结果
$ python3 argparse_uses_parent_with_group.py -h
usage: argparse_uses_parent_with_group.py [-h] [--user USER]
[--password PASSWORD]
[--local-arg]
optional arguments:
-h, --help show this help message and exit
--local-arg
authentication:
--user USER
--password PASSWORD
互斥选项
使用add_mutually_exclusive_group()可以添加互斥选项：
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())
执行结果
$ python3 argparse_mutually_exclusive.py -h
usage: argparse_mutually_exclusive.py [-h] [-a | -b]
optional arguments:
-h, --help show this help message and exit
-a
-b
$ python3 argparse_mutually_exclusive.py -a
Namespace(a=True, b=False)
$ python3 argparse_mutually_exclusive.py -b
Namespace(a=False, b=True)
$ python3 argparse_mutually_exclusive.py -a -b
usage: argparse_mutually_exclusive.py [-h] [-a | -b]
argparse_mutually_exclusive.py: error: argument -b: not allowed
with argument -a
嵌套解析
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())
执行结果
$ python3 argparse_subparsers.py -h
usage: argparse_subparsers.py [-h] {list,create,delete} ...
positional arguments:
{list,create,delete} commands
list List contents
create Create a directory
delete Remove a directory
optional arguments:
-h, --help show this help message and exit
$ python3 argparse_subparsers.py create -h
usage: argparse_subparsers.py create [-h] [--read-only] dirname
positional arguments:
dirname New directory to create
optional arguments:
-h, --help show this help message and exit
--read-only Set permissions to prevent writing to the directo
ry
$ python3 argparse_subparsers.py delete -r foo
Namespace(dirname='foo', recursive=True)
高级参数处理
可变参数：数字N代表N的参数，？0或者1个参数。*0或者多个参数。+1或者多个参数。
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())
执行结果
$ python3 argparse_nargs.py -h
usage: argparse_nargs.py [-h] [--three THREE THREE THREE]
[--optional [OPTIONAL]]
[--all [ALL [ALL ...]]]
[--one-or-more ONE_OR_MORE [ONE_OR_MORE ...]]
optional arguments:
-h, --help show this help message and exit
--three THREE THREE THREE
--optional [OPTIONAL]
--all [ALL [ALL ...]]
--one-or-more ONE_OR_MORE [ONE_OR_MORE ...]
$ python3 argparse_nargs.py
Namespace(all=None, one_or_more=None, optional=None, three=None)
$ python3 argparse_nargs.py --three
usage: argparse_nargs.py [-h] [--three THREE THREE THREE]
[--optional [OPTIONAL]]
[--all [ALL [ALL ...]]]
[--one-or-more ONE_OR_MORE [ONE_OR_MORE ...]]
argparse_nargs.py: error: argument --three: expected 3
argument(s)
$ python3 argparse_nargs.py --three a b c
Namespace(all=None, one_or_more=None, optional=None,
three=['a', 'b', 'c'])
$ python3 argparse_nargs.py --optional
Namespace(all=None, one_or_more=None, optional=None, three=None)
$ python3 argparse_nargs.py --optional with_value
Namespace(all=None, one_or_more=None, optional='with_value',
three=None)
$ python3 argparse_nargs.py --all with multiple values
Namespace(all=['with', 'multiple', 'values'], one_or_more=None,
optional=None, three=None)
$ python3 argparse_nargs.py --one-or-more with_value
Namespace(all=None, one_or_more=['with_value'], optional=None,
three=None)
$ python3 argparse_nargs.py --one-or-more with multiple values
Namespace(all=None, one_or_more=['with', 'multiple', 'values'],
optional=None, three=None)
$ python3 argparse_nargs.py --one-or-more
usage: argparse_nargs.py [-h] [--three THREE THREE THREE]
[--optional [OPTIONAL]]
[--all [ALL [ALL ...]]]
[--one-or-more ONE_OR_MORE [ONE_OR_MORE ...]]
argparse_nargs.py: error: argument --one-or-more: expected
at least one argument
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))
执行结果
$ python3 argparse_type.py -i 1
Namespace(f=None, file=None, i=1)
$ python3 argparse_type.py -f 3.14
Namespace(f=3.14, file=None, i=None)
$ python3 argparse_type.py --file argparse_type.py
Namespace(f=None, file=<_io.TextIOWrapper
name='argparse_type.py' mode='r' encoding='UTF-8'>, i=None)
$ python3 argparse_type.py -i a
usage: argparse_type.py [-h] [-i I] [-f F] [--file FILE]
argparse_type.py: error: argument -i: invalid int value: 'a'
$ python3 argparse_type.py -f 3.14.15
usage: argparse_type.py [-h] [-i I] [-f F] [--file FILE]
argparse_type.py: error: argument -f: invalid float value:
'3.14.15'
$ python3 argparse_type.py --file does_not_exist.txt
usage: argparse_type.py [-h] [-i I] [-f F] [--file FILE]
argparse_type.py: error: [Errno 2] No such file or directory:
'does_not_exist.txt'
Choices可以指定参数的选项：
argparse_choices.py
import argparse
parser = argparse.ArgumentParser()
parser.add_argument(
'--mode',
choices=('read-only', 'read-write'),
)
print(parser.parse_args())
执行结果
$ python3 argparse_choices.py -h
usage: argparse_choices.py [-h] [--mode {read-only,read-write}]
optional arguments:
-h, --help show this help message and exit
--mode {read-only,read-write}
$ python3 argparse_choices.py --mode read-only
Namespace(mode='read-only')
$ python3 argparse_choices.py --mode invalid
usage: argparse_choices.py [-h] [--mode {read-only,read-write}]
argparse_choices.py: error: argument --mode: invalid choice:
'invalid' (choose from 'read-only', 'read-write')
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))
执行结果
$ python3 argparse_FileType.py -h
usage: argparse_FileType.py [-h] [-i in-file] [-o out-file]
optional arguments:
-h, --help show this help message and exit
-i in-file
-o out-file
$ python3 argparse_FileType.py -i argparse_FileType.py -o tmp_\
file.txt
Input file: <_io.TextIOWrapper name='argparse_FileType.py'
mode='rt' encoding='UTF-8'>
Output file: <_io.TextIOWrapper name='tmp_file.txt' mode='wt'
encoding='UTF-8'>
$ python3 argparse_FileType.py -i no_such_file.txt
usage: argparse_FileType.py [-h] [-i in-file] [-o out-file]
argparse_FileType.py: error: argument -i: can't open
'no_such_file.txt': [Errno 2] No such file or directory:
'no_such_file.txt'
自定义action
自定义action是argparse.Action的子类可以处理add_argument中的参数定义相关的参数，并返回一个可调用对象。构造函数会处理参数定义，仅仅需要处理call函数。call函数中parser代表解释器，namespace用于返回解释结果，value为要处理的参数，option_string用于触发action（对可选参数，永远是None。
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)
执行结果
$ python3 argparse_custom_action.py
Initializing CustomAction
dest = 'a'
option_strings = ['-a']
required = False
Initializing CustomAction
dest = 'm'
nargs = '*'
option_strings = ['-m']
required = False
Processing CustomAction for a
parser = 4315836992
values = 'value'
option_string = '-a'
Processing CustomAction for m
parser = 4315836992
values = ['multivalue', 'second']
option_string = '-m'
Namespace(a='VALUE', m=['MULTIVALUE', 'SECOND'])
