A number of changes getting ready for a new ipcluster.

* Added argparse.py to IPython/external
* New reuse_furls options to ipcontroller.  By default the controller will now delete all
  old furl files unless the -r flag i given.  This is needed so engines starting up don't 
  pick up the old furl files.
* Minor logic changes in ipengine and engineconnector related to detecting errors relating
  to furl files.

IPython/external/argparse.py

@@ -0,0 +1,1867 b''
+# -*- coding: utf-8 -*-
+
+# Copyright � 2006 Steven J. Bethard <[e-mail]>.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted under the terms of the 3-clause BSD
+# license. No warranty expressed or implied.
+# For details, see the accompanying file LICENSE.txt.
+
+"""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 -- Formatter classes which
+        may be passed as the formatter_class= argument to the
+        ArgumentParser constructor. HelpFormatter is the default, while
+        RawDescriptionHelpFormatter tells the parser not to perform any
+        line-wrapping on description text.
+
+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__ = '0.8.0'
+
+import os as _os
+import re as _re
+import sys as _sys
+import textwrap as _textwrap
+
+from gettext import gettext as _
+
+SUPPRESS = '==SUPPRESS=='
+
+OPTIONAL = '?'
+ZERO_OR_MORE = '*'
+ONE_OR_MORE = '+'
+PARSER = '==PARSER=='
+
+# =============================
+# 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):
+
+    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, optionals, positionals, prefix=None):
+        if usage is not SUPPRESS:
+            args = usage, optionals, positionals, 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() % dict(prog=self._prog)
+        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, optionals, positionals, prefix):
+        if prefix is None:
+            prefix = _('usage: ')
+
+        # if no optionals or positionals are available, usage is just prog
+        if usage is None and not optionals and not positionals:
+            usage = '%(prog)s'
+            
+        # if optionals and positionals are available, calculate usage
+        elif usage is None:
+            usage = '%(prog)s' % dict(prog=self._prog)
+                
+            # determine width of "usage: PROG" and width of text
+            prefix_width = len(prefix) + len(usage) + 1
+            prefix_indent = self._current_indent + prefix_width
+            text_width = self._width - self._current_indent
+
+            # put them on one line if they're short enough
+            format = self._format_actions_usage
+            action_usage = format(optionals + positionals)
+            if prefix_width + len(action_usage) + 1 < text_width:
+                usage = '%s %s' % (usage, action_usage)
+            
+            # if they're long, wrap optionals and positionals individually
+            else:
+                optional_usage = format(optionals)
+                positional_usage = format(positionals)
+                indent = ' ' * prefix_indent
+
+                # usage is made of PROG, optionals and positionals
+                parts = [usage, ' ']
+                
+                # options always get added right after PROG
+                if optional_usage:
+                    parts.append(_textwrap.fill(
+                        optional_usage, text_width,
+                        initial_indent=indent,
+                        subsequent_indent=indent).lstrip())
+
+                # if there were options, put arguments on the next line
+                # otherwise, start them right after PROG
+                if positional_usage:
+                    part = _textwrap.fill(
+                        positional_usage, text_width,
+                        initial_indent=indent,
+                        subsequent_indent=indent).lstrip()
+                    if optional_usage:
+                        part = '\n' + indent + part
+                    parts.append(part)
+                usage = ''.join(parts)
+
+        # prefix with 'usage:'
+        return '%s%s\n\n' % (prefix, usage)
+
+    def _format_actions_usage(self, actions):
+        parts = []
+        for action in actions:
+            if action.help is SUPPRESS:
+                continue
+
+            # produce all arg strings        
+            if not action.option_strings:
+                parts.append(self._format_args(action, action.dest))
+
+            # 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
+                if not action.required:
+                    part = '[%s]' % part
+                parts.append(part)
+
+        return ' '.join(parts)
+
+    def _format_text(self, text):
+        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:
+            return self._format_metavar(action, action.dest)
+
+        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 _format_metavar(self, action, default_metavar):
+        if action.metavar is not None:
+            name = action.metavar
+        elif action.choices is not None:
+            choice_strs = (str(choice) for choice in action.choices)
+            name = '{%s}' % ','.join(choice_strs)
+        else:
+            name = default_metavar
+        return name
+
+    def _format_args(self, action, default_metavar):
+        name = self._format_metavar(action, default_metavar)
+        if action.nargs is None:
+            result = name
+        elif action.nargs == OPTIONAL:
+            result = '[%s]' % name
+        elif action.nargs == ZERO_OR_MORE:
+            result = '[%s [%s ...]]' % (name, name)
+        elif action.nargs == ONE_OR_MORE:
+            result = '%s [%s ...]' % (name, name)
+        elif action.nargs is PARSER:
+            result = '%s ...' % name
+        else:
+            result = ' '.join([name] * action.nargs)
+        return result
+
+    def _expand_help(self, action):
+        params = dict(vars(action), prog=self._prog)
+        for name, value in params.items():
+            if value is SUPPRESS:
+                del params[name]
+        if params.get('choices') is not None:
+            choices_str = ', '.join(str(c) for c in params['choices'])
+            params['choices'] = choices_str
+        return action.help % 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)
+
+class RawDescriptionHelpFormatter(HelpFormatter):
+    
+    def _fill_text(self, text, width, indent):
+        return ''.join(indent + line for line in text.splitlines(True))
+
+class RawTextHelpFormatter(RawDescriptionHelpFormatter):
+    
+    def _split_lines(self, text, width):
+        return text.splitlines()
+
+# =====================
+# Options and Arguments
+# =====================
+
+class ArgumentError(Exception):
+    """ArgumentError(message, argument)
+
+    Raised whenever there was an error 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):
+        if argument.option_strings:
+            self.argument_name =  '/'.join(argument.option_strings)
+        elif argument.metavar not in (None, SUPPRESS):
+            self.argument_name = argument.metavar
+        elif argument.dest not in (None, SUPPRESS):
+            self.argument_name = argument.dest
+        else:
+            self.argument_name = None
+        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)
+
+# ==============
+# Action classes
+# ==============
+
+class Action(_AttributeHolder):
+    """Action(*strings, **options)
+
+    Action objects hold the information necessary to convert a
+    set of command-line arguments (possibly including an initial option
+    string) into the desired Python object(s).
+
+    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 must be > 0')
+        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 must be > 0')
+        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):
+        _ensure_value(namespace, self.dest, []).append(values)
+
+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):
+        _ensure_value(namespace, self.dest, []).append(self.const)
+
+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,
+                 dest=SUPPRESS,
+                 default=SUPPRESS,
+                 help=None):
+        super(_VersionAction, 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_version()
+        parser.exit()
+        
+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 = {}
+        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
+        parser.parse_args(arg_strings, namespace)
+
+
+# ==============
+# 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=None):
+        self._mode = mode
+        self._bufsize = bufsize
+    
+    def __call__(self, string):
+        # the special argument "-" means sys.std{in,out}
+        if string == '-':
+            if self._mode == 'r':
+                return _sys.stdin
+            elif self._mode == 'w':
+                return _sys.stdout
+            else:
+                msg = _('argument "-" with mode %r' % self._mode)
+                raise ValueError(msg)
+
+        # all other arguments are used as file names
+        if self._bufsize:
+            return open(string, self._mode, self._bufsize)
+        else:
+            return open(string, self._mode)
+
+
+# ===========================
+# Optional and Positional Parsing
+# ===========================
+
+class Namespace(_AttributeHolder):
+
+    def __init__(self, **kwargs):
+        for name, value in kwargs.iteritems():
+            setattr(self, name, value)
+
+    def __eq__(self, other):
+        return vars(self) == vars(other)
+
+    def __ne__(self, other):
+        return not (self == other)
+
+
+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._optional_actions_list = []
+        self._positional_actions_list = []
+        self._positional_actions_full_list = []
+        self._option_strings = {}
+
+        # defaults storage
+        self._defaults = {}
+
+    # ====================
+    # 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 settings 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_list in [self._option_strings.values(),
+                            self._positional_actions_full_list]:
+            for action in action_list:
+                if action.dest in kwargs:
+                    action.default = kwargs[action.dest]
+
+    # =======================
+    # 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:
+            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)
+        action = action_class(**kwargs)
+        return self._add_action(action)
+
+    def _add_action(self, action):
+        # resolve any conflicts
+        self._check_conflict(action)
+
+        # add to optional or positional list
+        if action.option_strings:
+            self._optional_actions_list.append(action)
+        else:
+            self._positional_actions_list.append(action)
+            self._positional_actions_full_list.append(action)
+        action.container = self
+
+        # index the action by any option strings it has
+        for option_string in action.option_strings:
+            self._option_strings[option_string] = action
+
+        # return the created action
+        return action
+
+    def _add_container_actions(self, container):
+        for action in container._optional_actions_list:
+            self._add_action(action)
+        for action in container._positional_actions_list:
+            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)
+        
+        # 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 one-or-fewer-character option strings
+            if len(option_string) < 2:
+                msg = _('invalid option string %r: '
+                        'must be at least two characters long')
+                raise ValueError(msg % option_string)
+
+            # 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)
+
+            # error on strings that are all prefix characters
+            if not (set(option_string) - set(self.prefix_chars)):
+                msg = _('invalid option string %r: '
+                        'must contain characters other than %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 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_string.lstrip(self.prefix_chars)
+            dest = dest.replace('-', '_')
+
+        # return the updated keyword arguments
+        return dict(kwargs, dest=dest, option_strings=option_strings)
+
+    def _pop_action_class(self, kwargs, default=None):
+        action = kwargs.pop('action', default)
+        return self._registry_get('action', action, action)
+
+    def _get_handler(self):
+        # determine function from conflict handler string
+        handler_func_name = '_handle_conflict_%s' % self.conflict_handler
+        try:
+            return getattr(self, handler_func_name)
+        except AttributeError:
+            msg = _('invalid conflict_resolution value: %r')
+            raise ValueError(msg % self.conflict_handler)
+
+    def _check_conflict(self, action):
+
+        # find all options that conflict with this option        
+        confl_optionals = []
+        for option_string in action.option_strings:
+            if option_string in self._option_strings:
+                confl_optional = self._option_strings[option_string]
+                confl_optionals.append((option_string, confl_optional))
+
+        # resolve any conflicts
+        if confl_optionals:
+            conflict_handler = self._get_handler()
+            conflict_handler(action, confl_optionals)
+
+    def _handle_conflict_error(self, action, conflicting_actions):
+        message = _('conflicting option string(s): %s')
+        conflict_string = ', '.join(option_string
+                                    for option_string, action
+                                    in conflicting_actions)
+        raise ArgumentError(action, message % conflict_string)
+
+    def _handle_conflict_resolve(self, action, conflicting_actions):
+
+        # remove all conflicting options        
+        for option_string, action in conflicting_actions:
+            
+            # remove the conflicting option
+            action.option_strings.remove(option_string)
+            self._option_strings.pop(option_string, None)
+
+            # if the option now has no option string, remove it from the
+            # container holding it
+            if not action.option_strings:
+                action.container._optional_actions_list.remove(action)
+
+
+class _ArgumentGroup(_ActionsContainer):
+
+    def __init__(self, container, title=None, description=None, **kwargs):
+        # add any missing keyword arguments by checking the container
+        update = kwargs.setdefault
+        update('conflict_handler', container.conflict_handler)
+        update('prefix_chars', container.prefix_chars)
+        update('argument_default', container.argument_default)
+        super_init = super(_ArgumentGroup, self).__init__
+        super_init(description=description, **kwargs)
+        
+        self.title = title
+        self._registries = container._registries
+        self._positional_actions_full_list = container._positional_actions_full_list
+        self._option_strings = container._option_strings
+        self._defaults = container._defaults
+
+
+class ArgumentParser(_AttributeHolder, _ActionsContainer):
+
+    def __init__(self,
+                 prog=None,
+                 usage=None,
+                 description=None,
+                 epilog=None,
+                 version=None,
+                 parents=[],
+                 formatter_class=HelpFormatter,
+                 prefix_chars='-',
+                 argument_default=None,
+                 conflict_handler='error',
+                 add_help=True):
+
+        superinit = super(ArgumentParser, self).__init__
+        superinit(description=description,
+                  prefix_chars=prefix_chars,
+                  argument_default=argument_default,
+                  conflict_handler=conflict_handler)
+
+        # default setting for prog
+        if prog is None:
+            prog = _os.path.basename(_sys.argv[0])
+
+        self.prog = prog
+        self.usage = usage
+        self.epilog = epilog
+        self.version = version
+        self.formatter_class = formatter_class
+        self.add_help = add_help
+
+        self._argument_group_class = _ArgumentGroup
+        self._has_subparsers = False
+        self._argument_groups = []
+
+        # register types
+        def identity(string):
+            return string
+        self.register('type', None, identity)
+
+        # add help and version arguments if necessary
+        # (using explicit default to override global argument_default)
+        if self.add_help:
+            self.add_argument(
+                '-h', '--help', action='help', default=SUPPRESS,
+                help=_('show this help message and exit'))
+        if self.version:
+            self.add_argument(
+                '-v', '--version', action='version', default=SUPPRESS,
+                help=_("show program's version number and exit"))
+
+        # add parent arguments and defaults
+        for parent in parents:
+            self._add_container_actions(parent)
+            try:
+                defaults = parent._defaults
+            except AttributeError:
+                pass
+            else:
+                self._defaults.update(defaults)
+
+        # determines whether an "option" looks like a negative number
+        self._negative_number_matcher = _re.compile(r'^-\d+|-\d*.\d+$')
+                
+
+    # =======================
+    # Pretty __repr__ methods
+    # =======================
+
+    def _get_kwargs(self):
+        names = [
+            'prog',
+            'usage',
+            'description',
+            'version',
+            'formatter_class',
+            'conflict_handler',
+            'add_help',
+        ]
+        return [(name, getattr(self, name)) for name in names]
+
+    # ==================================
+    # Optional/Positional adding methods
+    # ==================================
+
+    def add_argument_group(self, *args, **kwargs):
+        group = self._argument_group_class(self, *args, **kwargs)
+        self._argument_groups.append(group)
+        return group
+
+    def add_subparsers(self, **kwargs):
+        if self._has_subparsers:
+            self.error(_('cannot have multiple subparser arguments'))
+        
+        # add the parser class to the arguments if it's not present
+        kwargs.setdefault('parser_class', type(self))
+
+        # prog defaults to the usage message of this parser, skipping
+        # optional arguments and with no "usage:" prefix
+        if kwargs.get('prog') is None:
+            formatter = self._get_formatter()
+            formatter.add_usage(self.usage, [],
+                                self._get_positional_actions(), '')
+            kwargs['prog'] = formatter.format_help().strip()
+
+        # create the parsers action and add it to the positionals list
+        parsers_class = self._pop_action_class(kwargs, 'parsers')
+        action = parsers_class(option_strings=[], **kwargs)
+        self._positional_actions_list.append(action)
+        self._positional_actions_full_list.append(action)
+        self._has_subparsers = True
+
+        # return the created parsers action
+        return action
+
+    def _add_container_actions(self, container):
+        super(ArgumentParser, self)._add_container_actions(container)
+        try:
+            groups = container._argument_groups
+        except AttributeError:
+            pass
+        else:
+            for group in groups:
+                new_group = self.add_argument_group(
+                    title=group.title,
+                    description=group.description,
+                    conflict_handler=group.conflict_handler)
+                new_group._add_container_actions(group)
+
+    def _get_optional_actions(self):
+        actions = []
+        actions.extend(self._optional_actions_list)
+        for argument_group in self._argument_groups:
+            actions.extend(argument_group._optional_actions_list)
+        return actions
+
+    def _get_positional_actions(self):
+        return list(self._positional_actions_full_list)
+
+
+    # =====================================
+    # Command line argument parsing methods
+    # =====================================
+
+    def parse_args(self, args=None, namespace=None):
+        # args default to the system args
+        if args is None:
+            args = _sys.argv[1:]
+
+        # default Namespace built from parser defaults
+        if namespace is None:
+            namespace = Namespace()
+            
+        # add any action defaults that aren't present
+        optional_actions = self._get_optional_actions()
+        positional_actions = self._get_positional_actions()
+        for action in optional_actions + positional_actions:
+            if action.dest is not SUPPRESS:
+                if not hasattr(namespace, action.dest):
+                    if action.default is not SUPPRESS:
+                        default = action.default
+                        if isinstance(action.default, basestring):
+                            default = self._get_value(action, default)
+                        setattr(namespace, action.dest, default)
+
+        # add any parser defaults that aren't present
+        for dest, value in self._defaults.iteritems():
+            if not hasattr(namespace, dest):
+                setattr(namespace, dest, value)
+            
+        # parse the arguments and exit if there are any errors
+        try:
+            result = self._parse_args(args, namespace)
+        except ArgumentError, err:
+            self.error(str(err))
+
+        # make sure all required optionals are present
+        for action in self._get_optional_actions():
+            if action.required:
+                if getattr(result, action.dest, None) is None:
+                    opt_strs = '/'.join(action.option_strings)
+                    msg = _('option %s is required' % opt_strs)
+                    self.error(msg)
+
+        # return the parsed arguments                    
+        return result
+
+    def _parse_args(self, arg_strings, namespace):            
+
+        # find all option indices, and determine the arg_string_pattern
+        # which has an 'O' if there is an option at an index,
+        # an 'A' if there is an argument, or a '-' if there is a '--'
+        option_string_indices = {}
+        arg_string_pattern_parts = []
+        arg_strings_iter = iter(arg_strings)
+        for i, arg_string in enumerate(arg_strings_iter):
+
+            # all args after -- are non-options
+            if arg_string == '--':
+                arg_string_pattern_parts.append('-')
+                for arg_string in arg_strings_iter:
+                    arg_string_pattern_parts.append('A')
+
+            # otherwise, add the arg to the arg strings
+            # and note the index if it was an option
+            else:
+                option_tuple = self._parse_optional(arg_string)
+                if option_tuple is None:
+                    pattern = 'A'
+                else:
+                    option_string_indices[i] = option_tuple
+                    pattern = 'O'
+                arg_string_pattern_parts.append(pattern)
+
+        # join the pieces together to form the pattern
+        arg_strings_pattern = ''.join(arg_string_pattern_parts)
+
+        # converts arg strings to the appropriate and then takes the action
+        def take_action(action, argument_strings, option_string=None):
+            argument_values = self._get_values(action, argument_strings)
+            # take the action if we didn't receive a SUPPRESS value
+            # (e.g. from a default)            
+            if argument_values is not SUPPRESS:
+                action(self, namespace, argument_values, option_string)
+
+        # function to convert arg_strings into an optional action
+        def consume_optional(start_index):
+            
+            # determine the optional action and parse any explicit
+            # argument out of the option string
+            option_tuple = option_string_indices[start_index]
+            action, option_string, explicit_arg = option_tuple
+
+            # loop because single-dash options can be chained
+            # (e.g. -xyz is the same as -x -y -z if no args are required)
+            match_argument = self._match_argument
+            action_tuples = []
+            while True:
+
+                # if we found no optional action, raise an error
+                if action is None:
+                    self.error(_('no such option: %s') % option_string)
+
+                # if there is an explicit argument, try to match the
+                # optional's string arguments to only this
+                if explicit_arg is not None:
+                    arg_count = match_argument(action, 'A')
+
+                    # if the action is a single-dash option and takes no
+                    # arguments, try to parse more single-dash options out
+                    # of the tail of the option string
+                    chars = self.prefix_chars
+                    if arg_count == 0 and option_string[1] not in chars:
+                        action_tuples.append((action, [], option_string))
+                        parse_optional = self._parse_optional
+                        for char in self.prefix_chars:
+                            option_string = char + explicit_arg
+                            option_tuple = parse_optional(option_string)
+                            if option_tuple[0] is not None:
+                                break
+                        else:
+                            msg = _('ignored explicit argument %r')
+                            raise ArgumentError(action, msg % explicit_arg)
+
+                        # set the action, etc. for the next loop iteration
+                        action, option_string, explicit_arg = option_tuple
+
+                    # if the action expect exactly one argument, we've
+                    # successfully matched the option; exit the loop
+                    elif arg_count == 1:
+                        stop = start_index + 1
+                        args = [explicit_arg]
+                        action_tuples.append((action, args, option_string))
+                        break
+
+                    # error if a double-dash option did not use the
+                    # explicit argument
+                    else:
+                        msg = _('ignored explicit argument %r')
+                        raise ArgumentError(action, msg % explicit_arg)
+                
+                # if there is no explicit argument, try to match the
+                # optional's string arguments with the following strings
+                # if successful, exit the loop
+                else:
+                    start = start_index + 1
+                    selected_patterns = arg_strings_pattern[start:]
+                    arg_count = match_argument(action, selected_patterns)
+                    stop = start + arg_count
+                    args = arg_strings[start:stop]
+                    action_tuples.append((action, args, option_string))
+                    break
+
+            # add the Optional to the list and return the index at which
+            # the Optional's string args stopped
+            assert action_tuples
+            for action, args, option_string in action_tuples:
+                take_action(action, args, option_string)
+            return stop
+
+        # the list of Positionals left to be parsed; this is modified
+        # by consume_positionals()
+        positionals = self._get_positional_actions()
+
+        # function to convert arg_strings into positional actions
+        def consume_positionals(start_index):
+            # match as many Positionals as possible
+            match_partial = self._match_arguments_partial
+            selected_pattern = arg_strings_pattern[start_index:]
+            arg_counts = match_partial(positionals, selected_pattern)
+
+            # slice off the appropriate arg strings for each Positional
+            # and add the Positional and its args to the list
+            for action, arg_count in zip(positionals, arg_counts):
+                args = arg_strings[start_index: start_index + arg_count]
+                start_index += arg_count
+                take_action(action, args)
+
+            # slice off the Positionals that we just parsed and return the
+            # index at which the Positionals' string args stopped
+            positionals[:] = positionals[len(arg_counts):]
+            return start_index
+
+        # consume Positionals and Optionals alternately, until we have
+        # passed the last option string
+        start_index = 0
+        if option_string_indices:
+            max_option_string_index = max(option_string_indices)
+        else:
+            max_option_string_index = -1
+        while start_index <= max_option_string_index:
+            
+            # consume any Positionals preceding the next option
+            next_option_string_index = min(
+                index
+                for index in option_string_indices
+                if index >= start_index)
+            if start_index != next_option_string_index:
+                positionals_end_index = consume_positionals(start_index)
+
+                # only try to parse the next optional if we didn't consume
+                # the option string during the positionals parsing
+                if positionals_end_index > start_index:
+                    start_index = positionals_end_index
+                    continue
+                else:
+                    start_index = positionals_end_index
+
+            # if we consumed all the positionals we could and we're not
+            # at the index of an option string, there were unparseable
+            # arguments
+            if start_index not in option_string_indices:
+                msg = _('extra arguments found: %s')
+                extras = arg_strings[start_index:next_option_string_index]
+                self.error(msg % ' '.join(extras))
+
+            # consume the next optional and any arguments for it
+            start_index = consume_optional(start_index)
+
+        # consume any positionals following the last Optional
+        stop_index = consume_positionals(start_index)
+
+        # if we didn't consume all the argument strings, there were too
+        # many supplied
+        if stop_index != len(arg_strings):
+            extras = arg_strings[stop_index:]
+            self.error(_('extra arguments found: %s') % ' '.join(extras))
+
+        # if we didn't use all the Positional objects, there were too few
+        # arg strings supplied.
+        if positionals:
+            self.error(_('too few arguments'))
+
+        # return the updated namespace
+        return namespace
+
+    def _match_argument(self, action, arg_strings_pattern):
+        # match the pattern for this action to the arg strings
+        nargs_pattern = self._get_nargs_pattern(action)
+        match = _re.match(nargs_pattern, arg_strings_pattern)
+
+        # raise an exception if we weren't able to find a match        
+        if match is None:
+            nargs_errors = {
+                None:_('expected one argument'),
+                OPTIONAL:_('expected at most one argument'),
+                ONE_OR_MORE:_('expected at least one argument')
+            }
+            default = _('expected %s argument(s)') % action.nargs
+            msg = nargs_errors.get(action.nargs, default)
+            raise ArgumentError(action, msg)
+
+        # return the number of arguments matched
+        return len(match.group(1))
+
+    def _match_arguments_partial(self, actions, arg_strings_pattern):
+        # progressively shorten the actions list by slicing off the
+        # final actions until we find a match
+        result = []
+        for i in xrange(len(actions), 0, -1):
+            actions_slice = actions[:i]
+            pattern = ''.join(self._get_nargs_pattern(action)
+                              for action in actions_slice)
+            match = _re.match(pattern, arg_strings_pattern)
+            if match is not None:
+                result.extend(len(string) for string in match.groups())
+                break
+
+        # return the list of arg string counts
+        return result
+    
+    def _parse_optional(self, arg_string):
+        # if it doesn't start with a prefix, it was meant to be positional
+        if not arg_string[0] in self.prefix_chars:
+            return None
+        
+        # if it's just dashes, it was meant to be positional
+        if not arg_string.strip('-'):
+            return None
+
+        # if the option string is present in the parser, return the action
+        if arg_string in self._option_strings:
+            action = self._option_strings[arg_string]
+            return action, arg_string, None
+
+        # search through all possible prefixes of the option string
+        # and all actions in the parser for possible interpretations
+        option_tuples = []
+        prefix_tuples = self._get_option_prefix_tuples(arg_string)
+        for option_string in self._option_strings:
+            for option_prefix, explicit_arg in prefix_tuples:
+                if option_string.startswith(option_prefix):
+                    action = self._option_strings[option_string]
+                    tup = action, option_string, explicit_arg
+                    option_tuples.append(tup)
+                    break
+
+        # if multiple actions match, the option string was ambiguous
+        if len(option_tuples) > 1:
+            options = ', '.join(opt_str for _, opt_str, _ in option_tuples)
+            tup = arg_string, options
+            self.error(_('ambiguous option: %s could match %s') % tup)
+
+        # if exactly one action matched, this segmentation is good,
+        # so return the parsed action
+        elif len(option_tuples) == 1:
+            option_tuple, = option_tuples
+            return option_tuple
+
+        # if it was not found as an option, but it looks like a negative
+        # number, it was meant to be positional
+        if self._negative_number_matcher.match(arg_string):
+            return None
+
+        # it was meant to be an optional but there is no such option
+        # in this parser (though it might be a valid option in a subparser)
+        return None, arg_string, None
+
+    def _get_option_prefix_tuples(self, option_string):
+        result = []
+        
+        # option strings starting with two prefix characters are only
+        # split at the '='
+        chars = self.prefix_chars
+        if option_string[0] in chars and option_string[1] in chars:
+            if '=' in option_string:
+                option_prefix, explicit_arg = option_string.split('=', 1)
+            else:
+                option_prefix = option_string
+                explicit_arg = None
+            tup = option_prefix, explicit_arg
+            result.append(tup)
+
+        # option strings starting with a single prefix character are
+        # split at all indices
+        else:
+            for first_index, char in enumerate(option_string):
+                if char not in self.prefix_chars:
+                    break
+            for i in xrange(len(option_string), first_index, -1):
+                tup = option_string[:i], option_string[i:] or None
+                result.append(tup)
+
+        # return the collected prefix tuples
+        return result                
+
+    def _get_nargs_pattern(self, action):
+        # in all examples below, we have to allow for '--' args
+        # which are represented as '-' in the pattern
+        nargs = action.nargs
+        
+        # the default (None) is assumed to be a single argument
+        if nargs is None:
+            nargs_pattern = '(-*A-*)'
+
+        # allow zero or one arguments
+        elif nargs == OPTIONAL:
+            nargs_pattern = '(-*A?-*)'
+
+        # allow zero or more arguments
+        elif nargs == ZERO_OR_MORE:
+            nargs_pattern = '(-*[A-]*)'
+
+        # allow one or more arguments
+        elif nargs == ONE_OR_MORE:
+            nargs_pattern = '(-*A[A-]*)'
+
+        # allow one argument followed by any number of options or arguments
+        elif nargs is PARSER:
+            nargs_pattern = '(-*A[-AO]*)'
+
+        # all others should be integers            
+        else:
+            nargs_pattern = '(-*%s-*)' % '-*'.join('A' * nargs)
+
+        # if this is an optional action, -- is not allowed        
+        if action.option_strings:
+            nargs_pattern = nargs_pattern.replace('-*', '')
+            nargs_pattern = nargs_pattern.replace('-', '')
+
+        # return the pattern
+        return nargs_pattern
+
+    # ========================
+    # Value conversion methods
+    # ========================
+
+    def _get_values(self, action, arg_strings):
+        # for everything but PARSER args, strip out '--'
+        if action.nargs is not PARSER:
+            arg_strings = [s for s in arg_strings if s != '--']
+        
+        # optional argument produces a default when not present
+        if not arg_strings and action.nargs == OPTIONAL:
+            if action.option_strings:
+                value = action.const
+            else:
+                value = action.default
+            if isinstance(value, basestring):
+                value = self._get_value(action, value)
+                self._check_value(action, value)
+
+        # when nargs='*' on a positional, if there were no command-line
+        # args, use the default if it is anything other than None
+        elif (not arg_strings and action.nargs == ZERO_OR_MORE and
+              not action.option_strings):
+            if action.default is not None:
+                value = action.default
+            else:
+                value = arg_strings
+            self._check_value(action, value)
+        
+        # single argument or optional argument produces a single value
+        elif len(arg_strings) == 1 and action.nargs in [None, OPTIONAL]:
+            arg_string, = arg_strings
+            value = self._get_value(action, arg_string)
+            self._check_value(action, value)
+
+        # PARSER arguments convert all values, but check only the first
+        elif action.nargs is PARSER:
+            value = list(self._get_value(action, v) for v in arg_strings)
+            self._check_value(action, value[0])
+
+        # all other types of nargs produce a list
+        else:
+            value = list(self._get_value(action, v) for v in arg_strings)
+            for v in value:
+                self._check_value(action, v)
+
+        # return the converted value            
+        return value
+
+    def _get_value(self, action, arg_string):
+        type_func = self._registry_get('type', action.type, action.type)
+        if not callable(type_func):
+            msg = _('%r is not callable')
+            raise ArgumentError(action, msg % type_func)
+        
+        # convert the value to the appropriate type
+        try:
+            result = type_func(arg_string)
+
+        # TypeErrors or ValueErrors indicate errors
+        except (TypeError, ValueError):
+            name = getattr(action.type, '__name__', repr(action.type))
+            msg = _('invalid %s value: %r')
+            raise ArgumentError(action, msg % (name, arg_string))
+
+        # return the converted value
+        return result
+
+    def _check_value(self, action, value):
+        # converted value must be one of the choices (if specified)
+        if action.choices is not None and value not in action.choices:
+            tup = value, ', '.join(map(repr, action.choices))
+            msg = _('invalid choice: %r (choose from %s)') % tup
+            raise ArgumentError(action, msg)
+
+        
+
+    # =======================
+    # Help-formatting methods
+    # =======================
+
+    def format_usage(self):
+        formatter = self._get_formatter()
+        formatter.add_usage(self.usage,
+                            self._get_optional_actions(),
+                            self._get_positional_actions())
+        return formatter.format_help()
+
+    def format_help(self):
+        formatter = self._get_formatter()
+
+        # usage
+        formatter.add_usage(self.usage,
+                            self._get_optional_actions(),
+                            self._get_positional_actions())
+
+        # description        
+        formatter.add_text(self.description)
+
+        # positionals
+        formatter.start_section(_('positional arguments'))
+        formatter.add_arguments(self._positional_actions_list)
+        formatter.end_section()
+
+        # optionals
+        formatter.start_section(_('optional arguments'))
+        formatter.add_arguments(self._optional_actions_list)
+        formatter.end_section()
+
+        # user-defined groups
+        for argument_group in self._argument_groups:
+            formatter.start_section(argument_group.title)
+            formatter.add_text(argument_group.description)
+            formatter.add_arguments(argument_group._positional_actions_list)
+            formatter.add_arguments(argument_group._optional_actions_list)
+            formatter.end_section()
+
+        # epilog
+        formatter.add_text(self.epilog)
+
+        # determine help from format above
+        return formatter.format_help()
+
+    def format_version(self):
+        formatter = self._get_formatter()
+        formatter.add_text(self.version)
+        return formatter.format_help()
+
+    def _get_formatter(self):
+        return self.formatter_class(prog=self.prog)
+
+    # =====================
+    # Help-printing methods
+    # =====================
+
+    def print_usage(self, file=None):
+        self._print_message(self.format_usage(), file)
+
+    def print_help(self, file=None):
+        self._print_message(self.format_help(), file)
+
+    def print_version(self, file=None):
+        self._print_message(self.format_version(), file)
+
+    def _print_message(self, message, file=None):
+        if message:
+            if file is None:
+                file = _sys.stderr
+            file.write(message)
+
+
+    # ===============
+    # Exiting methods
+    # ===============
+
+    def exit(self, status=0, message=None):
+        if message:
+            _sys.stderr.write(message)
+        _sys.exit(status)
+
+    def error(self, message):
+        """error(message: string)
+
+        Prints a usage message incorporating the message to stderr and
+        exits.
+        
+        If you override this in a subclass, it should not return -- it
+        should either exit or raise an exception.
+        """
+        self.print_usage(_sys.stderr)
+        self.exit(2, _('%s: error: %s\n') % (self.prog, message))

IPython/kernel/config/__init__.py

@@ -61,6 +61,7 b' controller_config = dict('
 
     logfile = '',    # Empty means log to stdout
     import_statement = '',
+    reuse_furls = False, # If False, old furl files are deleted
 
     engine_tub = dict(
         ip = '',         # Empty string means all interfaces

IPython/kernel/engineconnector.py

@@ -18,7 +18,8 b' __docformat__ = "restructuredtext en"'
 import os
 import cPickle as pickle
 
-from twisted.python import log
+from twisted.python import log, failure
+from twisted.internet import defer
 
 from IPython.kernel.fcutil import find_furl
 from IPython.kernel.enginefc import IFCEngine
@@ -62,13 +63,17 b' class EngineConnector(object):'
             self.tub.startService()
         self.engine_service = engine_service
         self.engine_reference = IFCEngine(self.engine_service)
-        self.furl = find_furl(furl_or_file)
+        try:
+            self.furl = find_furl(furl_or_file)
+        except ValueError:
+            return defer.fail(failure.Failure())
+            # return defer.fail(failure.Failure(ValueError('not a valid furl or furl file: %r' % furl_or_file)))
         d = self.tub.getReference(self.furl)
         d.addCallbacks(self._register, self._log_failure)
         return d
     
     def _log_failure(self, reason):
-        log.err('engine registration failed:')
+        log.err('EngineConnector: engine registration failed:')
         log.err(reason)
         return reason
 

IPython/kernel/scripts/ipcontroller.py

@@ -205,6 +205,17 b' def start_controller():'
         except:
             log.msg("Error running import_statement: %s" % cis)
     
+    # Delete old furl files unless the reuse_furls is set
+    reuse = config['controller']['reuse_furls']
+    if not reuse:
+        paths = (config['controller']['engine_furl_file'],
+            config['controller']['controller_interfaces']['task']['furl_file'],
+            config['controller']['controller_interfaces']['multiengine']['furl_file']
+        )
+        for p in paths:
+            if os.path.isfile(p):
+                os.remove(p)
+    
     # Create the service hierarchy
     main_service = service.MultiService()
     # The controller service
@@ -319,6 +330,12 b' def init_config():'
         dest="ipythondir",
         help="look for config files and profiles in this directory"
     )
+    parser.add_option(
+        "-r",
+        action="store_true",
+        dest="reuse_furls",
+        help="try to reuse all furl files"
+    )
     
     (options, args) = parser.parse_args()
     
@@ -352,6 +369,8 b' def init_config():'
         config['controller']['engine_tub']['cert_file'] = options.engine_cert_file
     if options.engine_furl_file is not None:
         config['controller']['engine_furl_file'] = options.engine_furl_file
+    if options.reuse_furls is not None:
+            config['controller']['reuse_furls'] = options.reuse_furls
 
     if options.logfile is not None:
         config['controller']['logfile'] = options.logfile

IPython/kernel/scripts/ipengine.py

@@ -107,7 +107,11 b' def start_engine():'
     furl_file = kernel_config['engine']['furl_file']
     log.msg("Using furl file: %s" % furl_file)
     d = engine_connector.connect_to_controller(engine_service, furl_file)
-    d.addErrback(lambda _: reactor.stop())
+    def handle_error(f):
+        log.err(f)
+        if reactor.running:
+            reactor.stop()
+    d.addErrback(handle_error)
     
     reactor.run()