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''' A decorator-based method of constructing IPython magics with `argparse`
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option handling.
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New magic functions can be defined like so::
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from IPython.core.magic_arguments import (argument, magic_arguments,
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parse_argstring)
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@magic_arguments()
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@argument('-o', '--option', help='An optional argument.')
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@argument('arg', type=int, help='An integer positional argument.')
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def magic_cool(self, arg):
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""" A really cool magic command.
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"""
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args = parse_argstring(magic_cool, arg)
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...
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The `@magic_arguments` decorator marks the function as having argparse arguments.
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The `@argument` decorator adds an argument using the same syntax as argparse's
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`add_argument()` method. More sophisticated uses may also require the
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`@argument_group` or `@kwds` decorator to customize the formatting and the
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parsing.
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Help text for the magic is automatically generated from the docstring and the
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arguments::
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In[1]: %cool?
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%cool [-o OPTION] arg
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A really cool magic command.
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positional arguments:
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arg An integer positional argument.
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optional arguments:
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-o OPTION, --option OPTION
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An optional argument.
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Here is an elaborated example that uses default parameters in `argument` and calls the `args` in the cell magic::
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from IPython.core.magic import register_cell_magic
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from IPython.core.magic_arguments import (argument, magic_arguments,
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parse_argstring)
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@magic_arguments()
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@argument(
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"--option",
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"-o",
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help=("Add an option here"),
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)
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@argument(
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"--style",
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"-s",
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default="foo",
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help=("Add some style arguments"),
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)
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@register_cell_magic
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def my_cell_magic(line, cell):
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args = parse_argstring(my_cell_magic, line)
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print(f"{args.option=}")
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print(f"{args.style=}")
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print(f"{cell=}")
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In a jupyter notebook, this cell magic can be executed like this::
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%%my_cell_magic -o Hello
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print("bar")
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i = 42
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Inheritance diagram:
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.. inheritance-diagram:: IPython.core.magic_arguments
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:parts: 3
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'''
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#-----------------------------------------------------------------------------
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# Copyright (C) 2010-2011, IPython Development Team.
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#
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# Distributed under the terms of the Modified BSD License.
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#
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# The full license is in the file COPYING.txt, distributed with this software.
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#-----------------------------------------------------------------------------
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import argparse
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import re
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# Our own imports
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from IPython.core.error import UsageError
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from IPython.utils.decorators import undoc
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from IPython.utils.process import arg_split
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from IPython.utils.text import dedent
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NAME_RE = re.compile(r"[a-zA-Z][a-zA-Z0-9_-]*$")
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@undoc
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class MagicHelpFormatter(argparse.RawDescriptionHelpFormatter):
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"""A HelpFormatter with a couple of changes to meet our needs.
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"""
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# Modified to dedent text.
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def _fill_text(self, text, width, indent):
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return argparse.RawDescriptionHelpFormatter._fill_text(self, dedent(text), width, indent)
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# Modified to wrap argument placeholders in <> where necessary.
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def _format_action_invocation(self, action):
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if not action.option_strings:
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metavar, = self._metavar_formatter(action, action.dest)(1)
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return metavar
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else:
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parts = []
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# if the Optional doesn't take a value, format is:
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# -s, --long
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if action.nargs == 0:
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parts.extend(action.option_strings)
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# if the Optional takes a value, format is:
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# -s ARGS, --long ARGS
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else:
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default = action.dest.upper()
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args_string = self._format_args(action, default)
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# IPYTHON MODIFICATION: If args_string is not a plain name, wrap
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# it in <> so it's valid RST.
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if not NAME_RE.match(args_string):
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args_string = "<%s>" % args_string
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for option_string in action.option_strings:
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parts.append('%s %s' % (option_string, args_string))
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return ', '.join(parts)
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# Override the default prefix ('usage') to our % magic escape,
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# in a code block.
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def add_usage(self, usage, actions, groups, prefix="::\n\n %"):
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super(MagicHelpFormatter, self).add_usage(usage, actions, groups, prefix)
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class MagicArgumentParser(argparse.ArgumentParser):
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""" An ArgumentParser tweaked for use by IPython magics.
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"""
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def __init__(self,
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prog=None,
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usage=None,
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description=None,
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epilog=None,
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parents=None,
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formatter_class=MagicHelpFormatter,
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prefix_chars='-',
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argument_default=None,
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conflict_handler='error',
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add_help=False):
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if parents is None:
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parents = []
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super(MagicArgumentParser, self).__init__(prog=prog, usage=usage,
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description=description, epilog=epilog,
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parents=parents, formatter_class=formatter_class,
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prefix_chars=prefix_chars, argument_default=argument_default,
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conflict_handler=conflict_handler, add_help=add_help)
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def error(self, message):
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""" Raise a catchable error instead of exiting.
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"""
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raise UsageError(message)
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def parse_argstring(self, argstring):
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""" Split a string into an argument list and parse that argument list.
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"""
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argv = arg_split(argstring)
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return self.parse_args(argv)
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def construct_parser(magic_func):
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""" Construct an argument parser using the function decorations.
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"""
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kwds = getattr(magic_func, 'argcmd_kwds', {})
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if 'description' not in kwds:
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kwds['description'] = getattr(magic_func, '__doc__', None)
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arg_name = real_name(magic_func)
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parser = MagicArgumentParser(arg_name, **kwds)
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# Reverse the list of decorators in order to apply them in the
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# order in which they appear in the source.
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group = None
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for deco in magic_func.decorators[::-1]:
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result = deco.add_to_parser(parser, group)
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if result is not None:
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group = result
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# Replace the magic function's docstring with the full help text.
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magic_func.__doc__ = parser.format_help()
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return parser
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def parse_argstring(magic_func, argstring):
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""" Parse the string of arguments for the given magic function.
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"""
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return magic_func.parser.parse_argstring(argstring)
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def real_name(magic_func):
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""" Find the real name of the magic.
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"""
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magic_name = magic_func.__name__
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if magic_name.startswith('magic_'):
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magic_name = magic_name[len('magic_'):]
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return getattr(magic_func, 'argcmd_name', magic_name)
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class ArgDecorator(object):
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""" Base class for decorators to add ArgumentParser information to a method.
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"""
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def __call__(self, func):
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if not getattr(func, 'has_arguments', False):
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func.has_arguments = True
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func.decorators = []
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func.decorators.append(self)
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return func
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def add_to_parser(self, parser, group):
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""" Add this object's information to the parser, if necessary.
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"""
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pass
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class magic_arguments(ArgDecorator):
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""" Mark the magic as having argparse arguments and possibly adjust the
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name.
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"""
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def __init__(self, name=None):
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self.name = name
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def __call__(self, func):
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if not getattr(func, 'has_arguments', False):
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func.has_arguments = True
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func.decorators = []
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if self.name is not None:
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func.argcmd_name = self.name
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# This should be the first decorator in the list of decorators, thus the
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# last to execute. Build the parser.
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func.parser = construct_parser(func)
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return func
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class ArgMethodWrapper(ArgDecorator):
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"""
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Base class to define a wrapper for ArgumentParser method.
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Child class must define either `_method_name` or `add_to_parser`.
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"""
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_method_name: str
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def __init__(self, *args, **kwds):
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self.args = args
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self.kwds = kwds
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def add_to_parser(self, parser, group):
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""" Add this object's information to the parser.
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"""
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if group is not None:
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parser = group
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getattr(parser, self._method_name)(*self.args, **self.kwds)
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return None
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class argument(ArgMethodWrapper):
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""" Store arguments and keywords to pass to add_argument().
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Instances also serve to decorate command methods.
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"""
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_method_name = 'add_argument'
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class defaults(ArgMethodWrapper):
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""" Store arguments and keywords to pass to set_defaults().
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Instances also serve to decorate command methods.
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"""
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_method_name = 'set_defaults'
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class argument_group(ArgMethodWrapper):
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""" Store arguments and keywords to pass to add_argument_group().
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Instances also serve to decorate command methods.
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"""
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def add_to_parser(self, parser, group):
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""" Add this object's information to the parser.
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"""
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return parser.add_argument_group(*self.args, **self.kwds)
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class kwds(ArgDecorator):
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""" Provide other keywords to the sub-parser constructor.
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"""
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def __init__(self, **kwds):
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self.kwds = kwds
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def __call__(self, func):
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func = super(kwds, self).__call__(func)
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func.argcmd_kwds = self.kwds
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return func
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__all__ = ['magic_arguments', 'argument', 'argument_group', 'kwds',
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'parse_argstring']
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