/External.LCA_RESTRICTED/Languages/CPython/27/Lib/argparse.py

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# Author: Steven J. Bethard <steven.bethard@gmail.com>.

"""Command-line parsing library

This module is an optparse-inspired command-line parsing library that:

    - handles both optional and positional arguments
    - produces highly informative usage messages
    - supports parsers that dispatch to sub-parsers

The following is a simple usage example that sums integers from the
command-line and writes the result to a file::

    parser = argparse.ArgumentParser(
        description='sum the integers at the command line')
    parser.add_argument(
        'integers', metavar='int', nargs='+', type=int,
        help='an integer to be summed')
    parser.add_argument(
        '--log', default=sys.stdout, type=argparse.FileType('w'),
        help='the file where the sum should be written')
    args = parser.parse_args()
    args.log.write('%s' % sum(args.integers))
    args.log.close()

The module contains the following public classes:

    - ArgumentParser -- The main entry point for command-line parsing. As the
        example above shows, the add_argument() method is used to populate
        the parser with actions for optional and positional arguments. Then
        the parse_args() method is invoked to convert the args at the
        command-line into an object with attributes.

    - ArgumentError -- The exception raised by ArgumentParser objects when
        there are errors with the parser's actions. Errors raised while
        parsing the command-line are caught by ArgumentParser and emitted
        as command-line messages.

    - FileType -- A factory for defining types of files to be created. As the
        example above shows, instances of FileType are typically passed as
        the type= argument of add_argument() calls.

    - Action -- The base class for parser actions. Typically actions are
        selected by passing strings like 'store_true' or 'append_const' to
        the action= argument of add_argument(). However, for greater
        customization of ArgumentParser actions, subclasses of Action may
        be defined and passed as the action= argument.

    - 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.

All other classes in this module are considered implementation details.
(Also note that HelpFormatter and RawDescriptionHelpFormatter are only
considered public as object names -- the API of the formatter objects is
still considered an implementation detail.)
"""

__version__ = '1.1'
__all__ = [
    'ArgumentParser',
    'ArgumentError',
    'ArgumentTypeError',
    'FileType',
    'HelpFormatter',
    'ArgumentDefaultsHelpFormatter',
    'RawDescriptionHelpFormatter',
    'RawTextHelpFormatter',
    'Namespace',
    'Action',
    'ONE_OR_MORE',
    'OPTIONAL',
    'PARSER',
    'REMAINDER',
    'SUPPRESS',
    'ZERO_OR_MORE',
]


import collections as _collections
import copy as _copy
import os as _os
import re as _re
import sys as _sys
import textwrap as _textwrap

from gettext import gettext as _


def _callable(obj):
    return hasattr(obj, '__call__') or hasattr(obj, '__bases__')


SUPPRESS = '==SUPPRESS=='

OPTIONAL = '?'
ZERO_OR_MORE = '*'
ONE_OR_MORE = '+'
PARSER = 'A...'
REMAINDER = '...'
_UNRECOGNIZED_ARGS_ATTR = '_unrecognized_args'

# =============================
# Utility functions and classes
# =============================

class _AttributeHolder(object):
    """Abstract base class that provides __repr__.

    The __repr__ method returns a string in the format::
        ClassName(attr=name, attr=name, ...)
    The attributes are determined either by a class-level attribute,
    '_kwarg_names', or by inspecting the instance __dict__.
    """

    def __repr__(self):
        type_name = type(self).__name__
        arg_strings = []
        for arg in self._get_args():
            arg_strings.append(repr(arg))
        for name, value in self._get_kwargs():
            arg_strings.append('%s=%r' % (name, value))
        return '%s(%s)' % (type_name, ', '.join(arg_strings))

    def _get_kwargs(self):
        return sorted(self.__dict__.items())

    def _get_args(self):
        return []


def _ensure_value(namespace, name, value):
    if getattr(namespace, name, None) is None:
        setattr(namespace, name, value)
    return getattr(namespace, name)


# ===============
# Formatting Help
# ===============

class HelpFormatter(object):
    """Formatter for generating usage messages and argument help strings.

    Only the name of this class is considered a public API. All the methods
    provided by the class are considered an implementation detail.
    """

    def __init__(self,
                 prog,
                 indent_increment=2,
                 max_help_position=24,
                 width=None):

        # default setting for width
        if width is None:
            try:
                width = int(_os.environ['COLUMNS'])
            except (KeyError, ValueError):
                width = 80
            width -= 2

        self._prog = prog
        self._indent_increment = indent_increment
        self._max_help_position = max_help_position
        self._width = width

        self._current_indent = 0
        self._level = 0
        self._action_max_length = 0

        self._root_section = self._Section(self, None)
        self._current_section = self._root_section

        self._whitespace_matcher = _re.compile(r'\s+')
        self._long_break_matcher = _re.compile(r'\n\n\n+')

    # ===============================
    # Section and indentation methods
    # ===============================
    def _indent(self):
        self._current_indent += self._indent_increment
        self._level += 1

    def _dedent(self):
        self._current_indent -= self._indent_increment
        assert self._current_indent >= 0, 'Indent decreased below 0.'
        self._level -= 1

    class _Section(object):

        def __init__(self, formatter, parent, heading=None):
            self.formatter = formatter
            self.parent = parent
            self.heading = heading
            self.items = []

        def format_help(self):
            # format the indented section
            if self.parent is not None:
                self.formatter._indent()
            join = self.formatter._join_parts
            for func, args in self.items:
                func(*args)
            item_help = join([func(*args) for func, args in self.items])
            if self.parent is not None:
                self.formatter._dedent()

            # return nothing if the section was empty
            if not item_help:
                return ''

            # add the heading if the section was non-empty
            if self.heading is not SUPPRESS and self.heading is not None:
                current_indent = self.formatter._current_indent
                heading = '%*s%s:\n' % (current_indent, '', self.heading)
            else:
                heading = ''

            # join the section-initial newline, the heading and the help
            return join(['\n', heading, item_help, '\n'])

    def _add_item(self, func, args):
        self._current_section.items.append((func, args))

    # ========================
    # Message building methods
    # ========================
    def start_section(self, heading):
        self._indent()
        section = self._Section(self, self._current_section, heading)
        self._add_item(section.format_help, [])
        self._current_section = section

    def end_section(self):
        self._current_section = self._current_section.parent
        self._dedent()

    def add_text(self, text):
        if text is not SUPPRESS and text is not None:
            self._add_item(self._format_text, [text])

    def add_usage(self, usage, actions, groups, prefix=None):
        if usage is not SUPPRESS:
            args = usage, actions, groups, prefix
            self._add_item(self._format_usage, args)

    def add_argument(self, action):
        if action.help is not SUPPRESS:

            # find all invocations
            get_invocation = self._format_action_invocation
            invocations = [get_invocation(action)]
            for subaction in self._iter_indented_subactions(action):
                invocations.append(get_invocation(subaction))

            # update the maximum item length
            invocation_length = max([len(s) for s in invocations])
            action_length = invocation_length + self._current_indent
            self._action_max_length = max(self._action_max_length,
                                          action_length)

            # add the item to the list
            self._add_item(self._format_action, [action])

    def add_arguments(self, actions):
        for action in actions:
            self.add_argument(action)

    # =======================
    # Help-formatting methods
    # =======================
    def format_help(self):
        help = self._root_section.format_help()
        if help:
            help = self._long_break_matcher.sub('\n\n', help)
            help = help.strip('\n') + '\n'
        return help

    def _join_parts(self, part_strings):
        return ''.join([part
                        for part in part_strings
                        if part and part is not SUPPRESS])

    def _format_usage(self, usage, actions, groups, prefix):
        if prefix is None:
            prefix = _('usage: ')

        # if usage is specified, use that
        if usage is not None:
            usage = usage % dict(prog=self._prog)

        # if no optionals or positionals are available, usage is just prog
        elif usage is None and not actions:
            usage = '%(prog)s' % dict(prog=self._prog)

        # if optionals and positionals are available, calculate usage
        elif usage is None:
            prog = '%(prog)s' % dict(prog=self._prog)

            # split optionals from positionals
            optionals = []
            positionals = []
            for action in actions:
                if action.option_strings:
                    optionals.append(action)
                else:
                    positionals.append(action)

            # build full usage string
            format = self._format_actions_usage
            action_usage = format(optionals + positionals, groups)
            usage = ' '.join([s for s in [prog, action_usage] if s])

            # wrap the usage parts if it's too long
            text_width = self._width - self._current_indent
            if len(prefix) + len(usage) > text_width:

                # break usage into wrappable parts
                part_regexp = r'\(.*?\)+|\[.*?\]+|\S+'
                opt_usage = format(optionals, groups)
                pos_usage = format(positionals, groups)
                opt_parts = _re.findall(part_regexp, opt_usage)
                pos_parts = _re.findall(part_regexp, pos_usage)
                assert ' '.join(opt_parts) == opt_usage
                assert ' '.join(pos_parts) == pos_usage

                # helper for wrapping lines
                def get_lines(parts, indent, prefix=None):
                    lines = []
                    line = []
                    if prefix is not None:
                        line_len = len(prefix) - 1
                    else:
                        line_len = len(indent) - 1
                    for part in parts:
                        if line_len + 1 + len(part) > text_width:
                            lines.append(indent + ' '.join(line))
                            line = []
                            line_len = len(indent) - 1
                        line.append(part)
                        line_len += len(part) + 1
                    if line:
                        lines.append(indent + ' '.join(line))
                    if prefix is not None:
                        lines[0] = lines[0][len(indent):]
                    return lines

                # if prog is short, follow it with optionals or positionals
                if len(prefix) + len(prog) <= 0.75 * text_width:
                    indent = ' ' * (len(prefix) + len(prog) + 1)
                    if opt_parts:
                        lines = get_lines([prog] + opt_parts, indent, prefix)
                        lines.extend(get_lines(pos_parts, indent))
                    elif pos_parts:
                        lines = get_lines([prog] + pos_parts, indent, prefix)
                    else:
                        lines = [prog]

                # if prog is long, put it on its own line
                else:
                    indent = ' ' * len(prefix)
                    parts = opt_parts + pos_parts
                    lines = get_lines(parts, indent)
                    if len(lines) > 1:
                        lines = []
                        lines.extend(get_lines(opt_parts, indent))
                        lines.extend(get_lines(pos_parts, indent))
                    lines = [prog] + lines

                # join lines into usage
                usage = '\n'.join(lines)

        # prefix with 'usage:'
        return '%s%s\n\n' % (prefix, usage)

    def _format_actions_usage(self, actions, groups):
        # find group indices and identify actions in groups
        group_actions = set()
        inserts = {}
        for group in groups:
            try:
                start = actions.index(group._group_actions[0])
            except ValueError:
                continue
            else:
                end = start + len(group._group_actions)
                if actions[start:end] == group._group_actions:
                    for action in group._group_actions:
                        group_actions.add(action)
                    if not group.required:
                        if start in inserts:
                            inserts[start] += ' ['
                        else:
                            inserts[start] = '['
                        inserts[end] = ']'
                    else:
                        if start in inserts:
                            inserts[start] += ' ('
                        else:
                            inserts[start] = '('
                        inserts[end] = ')'
                    for i in range(start + 1, end):
                        inserts[i] = '|'

        # collect all actions format strings
        parts = []
        for i, action in enumerate(actions):

            # suppressed arguments are marked with None
            # remove | separators for suppressed arguments
            if action.help is SUPPRESS:
                parts.append(None)
                if inserts.get(i) == '|':
                    inserts.pop(i)
                elif inserts.get(i + 1) == '|':
                    inserts.pop(i + 1)

            # produce all arg strings
            elif not action.option_strings:
                part = self._format_args(action, action.dest)

                # if it's in a group, strip the outer []
                if action in group_actions:
                    if part[0] == '[' and part[-1] == ']':
                        part = part[1:-1]

                # add the action string to the list
                parts.append(part)

            # produce the first way to invoke the option in brackets
            else:
                option_string = action.option_strings[0]

                # if the Optional doesn't take a value, format is:
                #    -s or --long
                if action.nargs == 0:
                    part = '%s' % option_string

                # if the Optional takes a value, format is:
                #    -s ARGS or --long ARGS
                else:
                    default = action.dest.upper()
                    args_string = self._format_args(action, default)
                    part = '%s %s' % (option_string, args_string)

                # make it look optional if it's not required or in a group
                if not action.required and action not in group_actions:
                    part = '[%s]' % part

                # add the action string to the list
                parts.append(part)

        # insert things at the necessary indices
        for i in sorted(inserts, reverse=True):
            parts[i:i] = [inserts[i]]

        # join all the action items with spaces
        text = ' '.join([item for item in parts if item is not None])

        # clean up separators for mutually exclusive groups
        open = r'[\[(]'
        close = r'[\])]'
        text = _re.sub(r'(%s) ' % open, r'\1', text)
        text = _re.sub(r' (%s)' % close, r'\1', text)
        text = _re.sub(r'%s *%s' % (open, close), r'', text)
        text = _re.sub(r'\(([^|]*)\)', r'\1', text)
        text = text.strip()

        # return the text
        return text

    def _format_text(self, text):
        if '%(prog)' in text:
            text = text % dict(prog=self._prog)
        text_width = self._width - self._current_indent
        indent = ' ' * self._current_indent
        return self._fill_text(text, text_width, indent) + '\n\n'

    def _format_action(self, action):
        # determine the required width and the entry label
        help_position = min(self._action_max_length + 2,
                            self._max_help_position)
        help_width = self._width - help_position
        action_width = help_position - self._current_indent - 2
        action_header = self._format_action_invocation(action)

        # ho nelp; start on same line and add a final newline
        if not action.help:
            tup = self._current_indent, '', action_header
            action_header = '%*s%s\n' % tup

        # short action name; start on the same line and pad two spaces
        elif len(action_header) <= action_width:
            tup = self._current_indent, '', action_width, action_header
            action_header = '%*s%-*s  ' % tup
            indent_first = 0

        # long action name; start on the next line
        else:
            tup = self._current_indent, '', action_header
            action_header = '%*s%s\n' % tup
            indent_first = help_position

        # collect the pieces of the action help
        parts = [action_header]

        # if there was help for the action, add lines of help text
        if action.help:
            help_text = self._expand_help(action)
            help_lines = self._split_lines(help_text, help_width)
            parts.append('%*s%s\n' % (indent_first, '', help_lines[0]))
            for line in help_lines[1:]:
                parts.append('%*s%s\n' % (help_position, '', line))

        # or add a newline if the description doesn't end with one
        elif not action_header.endswith('\n'):
            parts.append('\n')

        # if there are any sub-actions, add their help as well
        for subaction in self._iter_indented_subactions(action):
            parts.append(self._format_action(subaction))

        # return a single string
        return self._join_parts(parts)

    def _format_action_invocation(self, action):
        if not action.option_strings:
            metavar, = self._metavar_formatter(action, action.dest)(1)
            return metavar

        else:
            parts = []

            # if the Optional doesn't take a value, format is:
            #    -s, --long
            if action.nargs == 0:
                parts.extend(action.option_strings)

            # if the Optional takes a value, format is:
            #    -s ARGS, --long ARGS
            else:
                default = action.dest.upper()
                args_string = self._format_args(action, default)
                for option_string in action.option_strings:
                    parts.append('%s %s' % (option_string, args_string))

            return ', '.join(parts)

    def _metavar_formatter(self, action, default_metavar):
        if action.metavar is not None:
            result = action.metavar
        elif action.choices is not None:
            choice_strs = [str(choice) for choice in action.choices]
            result = '{%s}' % ','.join(choice_strs)
        else:
            result = default_metavar

        def format(tuple_size):
            if isinstance(result, tuple):
                return result
            else:
                return (result, ) * tuple_size
        return format

    def _format_args(self, action, default_metavar):
        get_metavar = self._metavar_formatter(action, default_metavar)
        if action.nargs is None:
            result = '%s' % get_metavar(1)
        elif action.nargs == OPTIONAL:
            result = '[%s]' % get_metavar(1)
        elif action.nargs == ZERO_OR_MORE:
            result = '[%s [%s ...]]' % get_metavar(2)
        elif action.nargs == ONE_OR_MORE:
            result = '%s [%s ...]' % get_metavar(2)
        elif action.nargs == REMAINDER:
            result = '...'
        elif action.nargs == PARSER:
            result = '%s ...' % get_metavar(1)
        else:
            formats = ['%s' for _ in range(action.nargs)]
            result = ' '.join(formats) % get_metavar(action.nargs)
        return result

    def _expand_help(self, action):
        params = dict(vars(action), prog=self._prog)
        for name in list(params):
            if params[name] is SUPPRESS:
                del params[name]
        for name in list(params):
            if hasattr(params[name], '__name__'):
                params[name] = params[name].__name__
        if params.get('choices') is not None:
            choices_str = ', '.join([str(c) for c in params['choices']])
            params['choices'] = choices_str
        return self._get_help_string(action) % params

    def _iter_indented_subactions(self, action):
        try:
            get_subactions = action._get_subactions
        except AttributeError:
            pass
        else:
            self._indent()
            for subaction in get_subactions():
                yield subaction
            self._dedent()

    def _split_lines(self, text, width):
        text = self._whitespace_matcher.sub(' ', text).strip()
        return _textwrap.wrap(text, width)

    def _fill_text(self, text, width, indent):
        text = self._whitespace_matcher.sub(' ', text).strip()
        return _textwrap.fill(text, width, initial_indent=indent,
                                           subsequent_indent=indent)

    def _get_help_string(self, action):
        return action.help


class RawDescriptionHelpFormatter(HelpFormatter):
    """Help message formatter which retains any formatting in descriptions.

    Only the name of this class is considered a public API. All the methods
    provided by the class are considered an implementation detail.
    """

    def _fill_text(self, text, width, indent):
        return ''.join([indent + line for line in text.splitlines(True)])


class RawTextHelpFormatter(RawDescriptionHelpFormatter):
    """Help message formatter which retains formatting of all help text.

    Only the name of this class is considered a public API. All the methods
    provided by the class are considered an implementation detail.
    """

    def _split_lines(self, text, width):
        return text.splitlines()


class ArgumentDefaultsHelpFormatter(HelpFormatter):
    """Help message formatter which adds default values to argument help.

    Only the name of this class is considered a public API. All the methods
    provided by the class are considered an implementation detail.
    """

    def _get_help_string(self, action):
        help = action.help
        if '%(default)' not in action.help:
            if action.default is not SUPPRESS:
                defaulting_nargs = [OPTIONAL, ZERO_OR_MORE]
                if action.option_strings or action.nargs in defaulting_nargs:
                    help += ' (default: %(default)s)'
        return help


# =====================
# Options and Arguments
# =====================

def _get_action_name(argument):
    if argument is None:
        return None
    elif argument.option_strings:
        return  '/'.join(argument.option_strings)
    elif argument.metavar not in (None, SUPPRESS):
        return argument.metavar
    elif argument.dest not in (None, SUPPRESS):
        return argument.dest
    else:
        return None


class ArgumentError(Exception):
    """An error from creating or using an argument (optional or positional).

    The string value of this exception is the message, augmented with
    information about the argument that caused it.
    """

    def __init__(self, argument, message):
        self.argument_name = _get_action_name(argument)
        self.message = message

    def __str__(self):
        if self.argument_name is None:
            format = '%(message)s'
        else:
            format = 'argument %(argument_name)s: %(message)s'
        return format % dict(message=self.message,
                             argument_name=self.argument_name)


class ArgumentTypeError(Exception):
    """An error from trying to convert a command line string to a type."""
    pass


# ==============
# Action classes
# ==============

class Action(_AttributeHolder):
    """Information about how to convert command line strings to Python objects.

    Action objects are used by an ArgumentParser to represent the information
    needed to parse a single argument from one or more strings from the
    command line. The keyword arguments to the Action constructor are also
    all attributes of Action instances.

    Keyword Arguments:

        - option_strings -- A list of command-line option strings which
            should be associated with this action.

        - dest -- The name of the attribute to hold the created object(s)

        - nargs -- The number of command-line arguments that should be
            consumed. By default, one argument will be consumed and a single
            value will be produced.  Other values include:
                - N (an integer) consumes N arguments (and produces a list)
                - '?' consumes zero or one arguments
                - '*' consumes zero or more arguments (and produces a list)
                - '+' consumes one or more arguments (and produces a list)
            Note that the difference between the default and nargs=1 is that
            with the default, a single value will be produced, while with
            nargs=1, a list containing a single value will be produced.

        - const -- The value to be produced if the option is specified and the
            option uses an action that takes no values.

        - default -- The value to be produced if the option is not specified.

        - type -- The type which the command-line arguments should be converted
            to, should be one of 'string', 'int', 'float', 'complex' or a
            callable object that accepts a single string argument. If None,
            'string' is assumed.

        - choices -- A container of values that should be allowed. If not None,
            after a command-line argument has been converted to the appropriate
            type, an exception will be raised if it is not a member of this
            collection.

        - required -- True if the action must always be specified at the
            command line. This is only meaningful for optional command-line
            arguments.

        - help -- The help string describing the argument.

        - metavar -- The name to be used for the option's argument with the
            help string. If None, the 'dest' value will be used as the name.
    """

    def __init__(self,
                 option_strings,
                 dest,
                 nargs=None,
                 const=None,
                 default=None,
                 type=None,
                 choices=None,
                 required=False,
                 help=None,
                 metavar=None):
        self.option_strings = option_strings
        self.dest = dest
        self.nargs = nargs
        self.const = const
        self.default = default
        self.type = type
        self.choices = choices
        self.required = required
        self.help = help
        self.metavar = metavar

    def _get_kwargs(self):
        names = [
            'option_strings',
            'dest',
            'nargs',
            'const',
            'default',
            'type',
            'choices',
            'help',
            'metavar',
        ]
        return [(name, getattr(self, name)) for name in names]

    def __call__(self, parser, namespace, values, option_string=None):
        raise NotImplementedError(_('.__call__() not defined'))


class _StoreAction(Action):

    def __init__(self,
                 option_strings,
                 dest,
                 nargs=None,
                 const=None,
                 default=None,
                 type=None,
                 choices=None,
                 required=False,
                 help=None,
                 metavar=None):
        if nargs == 0:
            raise ValueError('nargs for store actions must be > 0; if you '
                             'have nothing to store, actions such as store '
                             'true or store const may be more appropriate')
        if const is not None and nargs != OPTIONAL:
            raise ValueError('nargs must be %r to supply const' % OPTIONAL)
        super(_StoreAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            nargs=nargs,
            const=const,
            default=default,
            type=type,
            choices=choices,
            required=required,
            help=help,
            metavar=metavar)

    def __call__(self, parser, namespace, values, option_string=None):
        setattr(namespace, self.dest, values)


class _StoreConstAction(Action):

    def __init__(self,
                 option_strings,
                 dest,
                 const,
                 default=None,
                 required=False,
                 help=None,
                 metavar=None):
        super(_StoreConstAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            nargs=0,
            const=const,
            default=default,
            required=required,
            help=help)

    def __call__(self, parser, namespace, values, option_string=None):
        setattr(namespace, self.dest, self.const)


class _StoreTrueAction(_StoreConstAction):

    def __init__(self,
                 option_strings,
                 dest,
                 default=False,
                 required=False,
                 help=None):
        super(_StoreTrueAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            const=True,
            default=default,
            required=required,
            help=help)


class _StoreFalseAction(_StoreConstAction):

    def __init__(self,
                 option_strings,
                 dest,
                 default=True,
                 required=False,
                 help=None):
        super(_StoreFalseAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            const=False,
            default=default,
            required=required,
            help=help)


class _AppendAction(Action):

    def __init__(self,
                 option_strings,
                 dest,
                 nargs=None,
                 const=None,
                 default=None,
                 type=None,
                 choices=None,
                 required=False,
                 help=None,
                 metavar=None):
        if nargs == 0:
            raise ValueError('nargs for append actions must be > 0; if arg '
                             'strings are not supplying the value to append, '
                             'the append const action may be more appropriate')
        if const is not None and nargs != OPTIONAL:
            raise ValueError('nargs must be %r to supply const' % OPTIONAL)
        super(_AppendAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            nargs=nargs,
            const=const,
            default=default,
            type=type,
            choices=choices,
            required=required,
            help=help,
            metavar=metavar)

    def __call__(self, parser, namespace, values, option_string=None):
        items = _copy.copy(_ensure_value(namespace, self.dest, []))
        items.append(values)
        setattr(namespace, self.dest, items)


class _AppendConstAction(Action):

    def __init__(self,
                 option_strings,
                 dest,
                 const,
                 default=None,
                 required=False,
                 help=None,
                 metavar=None):
        super(_AppendConstAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            nargs=0,
            const=const,
            default=default,
            required=required,
            help=help,
            metavar=metavar)

    def __call__(self, parser, namespace, values, option_string=None):
        items = _copy.copy(_ensure_value(namespace, self.dest, []))
        items.append(self.const)
        setattr(namespace, self.dest, items)


class _CountAction(Action):

    def __init__(self,
                 option_strings,
                 dest,
                 default=None,
                 required=False,
                 help=None):
        super(_CountAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            nargs=0,
            default=default,
            required=required,
            help=help)

    def __call__(self, parser, namespace, values, option_string=None):
        new_count = _ensure_value(namespace, self.dest, 0) + 1
        setattr(namespace, self.dest, new_count)


class _HelpAction(Action):

    def __init__(self,
                 option_strings,
                 dest=SUPPRESS,
                 default=SUPPRESS,
                 help=None):
        super(_HelpAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            default=default,
            nargs=0,
            help=help)

    def __call__(self, parser, namespace, values, option_string=None):
        parser.print_help()
        parser.exit()


class _VersionAction(Action):

    def __init__(self,
                 option_strings,
                 version=None,
                 dest=SUPPRESS,
                 default=SUPPRESS,
                 help="show program's version number and exit"):
        super(_VersionAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            default=default,
            nargs=0,
            help=help)
        self.version = version

    def __call__(self, parser, namespace, values, option_string=None):
        version = self.version
        if version is None:
            version = parser.version
        formatter = parser._get_formatter()
        formatter.add_text(version)
        parser.exit(message=formatter.format_help())


class _SubParsersAction(Action):

    class _ChoicesPseudoAction(Action):

        def __init__(self, name, help):
            sup = super(_SubParsersAction._ChoicesPseudoAction, self)
            sup.__init__(option_strings=[], dest=name, help=help)

    def __init__(self,
                 option_strings,
                 prog,
                 parser_class,
                 dest=SUPPRESS,
                 help=None,
                 metavar=None):

        self._prog_prefix = prog
        self._parser_class = parser_class
        self._name_parser_map = _collections.OrderedDict()
        self._choices_actions = []

        super(_SubParsersAction, self).__init__(
            option_strings=option_strings,
            dest=dest,
            nargs=PARSER,
            choices=self._name_parser_map,
            help=help,
            metavar=metavar)

    def add_parser(self, name, **kwargs):
        # set prog from the existing prefix
        if kwargs.get('prog') is None:
            kwargs['prog'] = '%s %s' % (self._prog_prefix, name)

        # create a pseudo-action to hold the choice help
        if 'help' in kwargs:
            help = kwargs.pop('help')
            choice_action = self._ChoicesPseudoAction(name, help)
            self._choices_actions.append(choice_action)

        # create the parser and add it to the map
        parser = self._parser_class(**kwargs)
        self._name_parser_map[name] = parser
        return parser

    def _get_subactions(self):
        return self._choices_actions

    def __call__(self, parser, namespace, values, option_string=None):
        parser_name = values[0]
        arg_strings = values[1:]

        # set the parser name if requested
        if self.dest is not SUPPRESS:
            setattr(namespace, self.dest, parser_name)

        # select the parser
        try:
            parser = self._name_parser_map[parser_name]
        except KeyError:
            tup = parser_name, ', '.join(self._name_parser_map)
            msg = _('unknown parser %r (choices: %s)') % tup
            raise ArgumentError(self, msg)

        # parse all the remaining options into the namespace
        # store any unrecognized options on the object, so that the top
        # level parser can decide what to do with them
        namespace, arg_strings = parser.parse_known_args(arg_strings, namespace)
        if arg_strings:
            vars(namespace).setdefault(_UNRECOGNIZED_ARGS_ATTR, [])
            getattr(namespace, _UNRECOGNIZED_ARGS_ATTR).extend(arg_strings)


# ==============
# Type classes
# ==============

class FileType(object):
    """Factory for creating file object types

    Instances of FileType are typically passed as type= arguments to the
    ArgumentParser add_argument() method.

    Keyword Arguments:
        - mode -- A string indicating how the file is to be opened. Accepts the
            same values as the builtin open() function.
        - bufsize -- The file's desired buffer size. Accepts the same values as
            the builtin open() function.
    """

    def __init__(self, mode='r', bufsize=-1):
        self._mode = mode
        self._bufsize = bufsize

    def __call__(self, string):
        # the special argument "-" means sys.std{in,out}
        if string == '-':
            if 'r' in self._mode:
                return _sys.stdin
            elif 'w' in self._mode:
                return _sys.stdout
            else:
                msg = _('argument "-" with mode %r') % self._mode
                raise ValueError(msg)

        # all other arguments are used as file names
        try:
            return open(string, self._mode, self._bufsize)
        except IOError as e:
            message = _("can't open '%s': %s")
            raise ArgumentTypeError(message % (string, e))

    def __repr__(self):
        args = self._mode, self._bufsize
        args_str = ', '.join(repr(arg) for arg in args if arg != -1)
        return '%s(%s)' % (type(self).__name__, args_str)

# ===========================
# Optional and Positional Parsing
# ===========================

class Namespace(_AttributeHolder):
    """Simple object for storing attributes.

    Implements equality by attribute names and values, and provides a simple
    string representation.
    """

    def __init__(self, **kwargs):
        for name in kwargs:
            setattr(self, name, kwargs[name])

    __hash__ = None

    def __eq__(self, other):
        return vars(self) == vars(other)

    def __ne__(self, other):
        return not (self == other)

    def __contains__(self, key):
        return key in self.__dict__


class _ActionsContainer(object):

    def __init__(self,
                 description,
                 prefix_chars,
                 argument_default,
                 conflict_handler):
        super(_ActionsContainer, self).__init__()

        self.description = description
        self.argument_default = argument_default
        self.prefix_chars = prefix_chars
        self.conflict_handler = conflict_handler

        # set up registries
        self._registries = {}

        # register actions
        self.register('action', None, _StoreAction)
        self.register('action', 'store', _StoreAction)
        self.register('action', 'store_const', _StoreConstAction)
        self.register('action', 'store_true', _StoreTrueAction)
        self.register('action', 'store_false', _StoreFalseAction)
        self.register('action', 'append', _AppendAction)
        self.register('action', 'append_const', _AppendConstAction)
        self.register('action', 'count', _CountAction)
        self.register('action', 'help', _HelpAction)
        self.register('action', 'version', _VersionAction)
        self.register('action', 'parsers', _SubParsersAction)

        # raise an exception if the conflict handler is invalid
        self._get_handler()

        # action storage
        self._actions = []
        self._option_string_actions = {}

        # groups
        self._action_groups = []
        self._mutually_exclusive_groups = []

        # defaults storage
        self._defaults = {}

        # determines whether an "option" looks like a negative number
        self._negative_number_matcher = _re.compile(r'^-\d+$|^-\d*\.\d+$')

        # whether or not there are any optionals that look like negative
        # numbers -- uses a list so it can be shared and edited
        self._has_negative_number_optionals = []

    # ====================
    # Registration methods
    # ====================
    def register(self, registry_name, value, object):
        registry = self._registries.setdefault(registry_name, {})
        registry[value] = object

    def _registry_get(self, registry_name, value, default=None):
        return self._registries[registry_name].get(value, default)

    # ==================================
    # Namespace default accessor methods
    # ==================================
    def set_defaults(self, **kwargs):
        self._defaults.update(kwargs)

        # if these defaults match any existing arguments, replace
        # the previous default on the object with the new one
        for action in self._actions:
            if action.dest in kwargs:
                action.default = kwargs[action.dest]

    def get_default(self, dest):
        for action in self._actions:
            if action.dest == dest and action.default is not None:
                return action.default
        return self._defaults.get(dest, None)


    # =======================
    # Adding argument actions
    # =======================
    def add_argument(self, *args, **kwargs):
        """
        add_argument(dest, ..., name=value, ...)
        add_argument(option_string, option_string, ..., name=value, ...)
        """

        # if no positional args are supplied or only one is supplied and
        # it doesn't look like an option string, parse a positional
        # argument
        chars = self.prefix_chars
        if not args or len(args) == 1 and args[0][0] not in chars:
            if args and 'dest' in kwargs:
                raise ValueError('dest supplied twice for positional argument')
            kwargs = self._get_positional_kwargs(*args, **kwargs)

        # otherwise, we're adding an optional argument
        else:
            kwargs = self._get_optional_kwargs(*args, **kwargs)

        # if no default was supplied, use the parser-level default
        if 'default' not in kwargs:
            dest = kwargs['dest']
            if dest in self._defaults:
                kwargs['default'] = self._defaults[dest]
            elif self.argument_default is not None:
                kwargs['default'] = self.argument_default

        # create the action object, and add it to the parser
        action_class = self._pop_action_class(kwargs)
        if not _callable(action_class):
            raise ValueError('unknown action "%s"' % (action_class,))
        action = action_class(**kwargs)

        # raise an error if the action type is not callable
        type_func = self._registry_get('type', action.type, action.type)
        if not _callable(type_func):
            raise ValueError('%r is not callable' % (type_func,))

        # raise an error if the metavar does not match the type
        if hasattr(self, "_get_formatter"):
            try:
                self._get_formatter()._format_args(action, None)
            except TypeError:
                raise ValueError("length of metavar tuple does not match nargs")

        return self._add_action(action)

    def add_argument_group(self, *args, **kwargs):
        group = _ArgumentGroup(self, *args, **kwargs)
        self._action_groups.append(group)
        return group

    def add_mutually_exclusive_group(self, **kwargs):
        group = _MutuallyExclusiveGroup(self, **kwargs)
        self._mutually_exclusive_groups.append(group)
        return group

    def _add_action(self, action):
        # resolve any conflicts
        self._check_conflict(action)

        # add to actions list
        self._actions.append(action)
        action.container = self

        # index the action by any option strings it has
        for option_string in action.option_strings:
            self._option_string_actions[option_string] = action

        # set the flag if any option strings look like negative numbers
        for option_string in action.option_strings:
            if self._negative_number_matcher.match(option_string):
                if not self._has_negative_number_optionals:
                    self._has_negative_number_optionals.append(True)

        # return the created action
        return action

    def _remove_action(self, action):
        self._actions.remove(action)

    def _add_container_actions(self, container):
        # collect groups by titles
        title_group_map = {}
        for group in self._action_groups:
            if group.title in title_group_map:
                msg = _('cannot merge actions - two groups are named %r')
                raise ValueError(msg % (group.title))
            title_group_map[group.title] = group

        # map each action to its group
        group_map = {}
        for group in container._action_groups:

            # if a group with the title exists, use that, otherwise
            # create a new group matching the container's group
            if group.title not in title_group_map:
                title_group_map[group.title] = self.add_argument_group(
                    title=group.title,
                    description=group.description,
                    conflict_handler=group.conflict_handler)

            # map the actions to their new group
            for action in group._group_actions:
                group_map[action] = title_group_map[group.title]

        # add container's mutually exclusive groups
        # NOTE: if add_mutually_exclusive_group ever gains title= and
        # description= then this code will need to be expanded as above
        for group in container._mutually_exclusive_groups:
            mutex_group = self.add_mutually_exclusive_group(
                required=group.required)

            # map the actions to their new mutex group
            for action in group._group_actions:
                group_map[action] = mutex_group

        # add all actions to this container or their group
        for action in container._actions:
            group_map.get(action, self)._add_action(action)

    def _get_positional_kwargs(self, dest, **kwargs):
        # make sure required is not specified
        if 'required' in kwargs:
            msg = _("'required' is an invalid argument for positionals")
            raise TypeError(msg)

        # mark positional arguments as required if at least one is
        # always required
        if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE]:
            kwargs['required'] = True
        if kwargs.get('nargs') == ZERO_OR_MORE and 'default' not in kwargs:
            kwargs['required'] = True

        # return the keyword arguments with no option strings
        return dict(kwargs, dest=dest, option_strings=[])

    def _get_optional_kwargs(self, *args, **kwargs):
        # determine short and long option strings
        option_strings = []
        long_option_strings = []
        for option_string in args:
            # error on strings that don't start with an appropriate prefix
            if not option_string[0] in self.prefix_chars:
                msg = _('invalid option string %r: '
                        'must start with a character %r')
                tup = option_string, self.prefix_chars
                raise ValueError(msg % tup)

            # strings starting with two prefix characters are long options
            option_strings.append(option_string)
            if option_string[0] in self.prefix_chars:
                if len(option_string) > 1:
                    if option_string[1] in self.prefix_chars:
                        long_option_strings.append(option_string)

        # infer destination, '--foo-bar' -> 'foo_bar' and '-x' -> 'x'
        dest = kwargs.pop('dest', None)
        if dest is None:
            if long_option_strings:
                dest_option_string = long_option_strings[0]
            else:
                dest_option_string = option_strings[0]
            dest = dest_option_str…