From 3f66309538f8393e15449aa1380430457ed864b7 Mon Sep 17 00:00:00 2001
From: Pierre <ratinaud@univ-tlse2.fr>
Date: Sat, 24 Nov 2012 15:43:52 +0100
Subject: [PATCH 1/1] add new configparser

---
 configparser.py         | 1313 +++++++++++++++++++++++++++++++++++++++++++++++
 configparser_helpers.py |  134 +++++
 2 files changed, 1447 insertions(+)
 create mode 100644 configparser.py
 create mode 100644 configparser_helpers.py

diff --git a/configparser.py b/configparser.py
new file mode 100644
index 0000000..8e6280d
--- /dev/null
+++ b/configparser.py
@@ -0,0 +1,1313 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+u"""Configuration file parser.
+
+A configuration file consists of sections, lead by a "[section]" header,
+and followed by "name: value" entries, with continuations and such in
+the style of RFC 822.
+
+Intrinsic defaults can be specified by passing them into the
+ConfigParser constructor as a dictionary.
+
+class:
+
+ConfigParser -- responsible for parsing a list of
+                    configuration files, and managing the parsed database.
+
+    methods:
+
+    __init__(defaults=None, dict_type=_default_dict, allow_no_value=False,
+             delimiters=('=', ':'), comment_prefixes=('#', ';'),
+             inline_comment_prefixes=None, strict=True,
+             empty_lines_in_values=True):
+        Create the parser. When `defaults' is given, it is initialized into the
+        dictionary or intrinsic defaults. The keys must be strings, the values
+        must be appropriate for %()s string interpolation.
+
+        When `dict_type' is given, it will be used to create the dictionary
+        objects for the list of sections, for the options within a section, and
+        for the default values.
+
+        When `delimiters' is given, it will be used as the set of substrings
+        that divide keys from values.
+
+        When `comment_prefixes' is given, it will be used as the set of
+        substrings that prefix comments in empty lines. Comments can be
+        indented.
+
+        When `inline_comment_prefixes' is given, it will be used as the set of
+        substrings that prefix comments in non-empty lines.
+
+        When `strict` is True, the parser won't allow for any section or option
+        duplicates while reading from a single source (file, string or
+        dictionary). Default is True.
+
+        When `empty_lines_in_values' is False (default: True), each empty line
+        marks the end of an option. Otherwise, internal empty lines of
+        a multiline option are kept as part of the value.
+
+        When `allow_no_value' is True (default: False), options without
+        values are accepted; the value presented for these is None.
+
+    sections()
+        Return all the configuration section names, sans DEFAULT.
+
+    has_section(section)
+        Return whether the given section exists.
+
+    has_option(section, option)
+        Return whether the given option exists in the given section.
+
+    options(section)
+        Return list of configuration options for the named section.
+
+    read(filenames, encoding=None)
+        Read and parse the list of named configuration files, given by
+        name.  A single filename is also allowed.  Non-existing files
+        are ignored.  Return list of successfully read files.
+
+    read_file(f, filename=None)
+        Read and parse one configuration file, given as a file object.
+        The filename defaults to f.name; it is only used in error
+        messages (if f has no `name' attribute, the string `<???>' is used).
+
+    read_string(string)
+        Read configuration from a given string.
+
+    read_dict(dictionary)
+        Read configuration from a dictionary. Keys are section names,
+        values are dictionaries with keys and values that should be present
+        in the section. If the used dictionary type preserves order, sections
+        and their keys will be added in order. Values are automatically
+        converted to strings.
+
+    get(section, option, raw=False, vars=None, fallback=_UNSET)
+        Return a string value for the named option.  All % interpolations are
+        expanded in the return values, based on the defaults passed into the
+        constructor and the DEFAULT section.  Additional substitutions may be
+        provided using the `vars' argument, which must be a dictionary whose
+        contents override any pre-existing defaults. If `option' is a key in
+        `vars', the value from `vars' is used.
+
+    getint(section, options, raw=False, vars=None, fallback=_UNSET)
+        Like get(), but convert value to an integer.
+
+    getfloat(section, options, raw=False, vars=None, fallback=_UNSET)
+        Like get(), but convert value to a float.
+
+    getboolean(section, options, raw=False, vars=None, fallback=_UNSET)
+        Like get(), but convert value to a boolean (currently case
+        insensitively defined as 0, false, no, off for False, and 1, true,
+        yes, on for True).  Returns False or True.
+
+    items(section=_UNSET, raw=False, vars=None)
+        If section is given, return a list of tuples with (section_name,
+        section_proxy) for each section, including DEFAULTSECT. Otherwise,
+        return a list of tuples with (name, value) for each option
+        in the section.
+
+    remove_section(section)
+        Remove the given file section and all its options.
+
+    remove_option(section, option)
+        Remove the given option from the given section.
+
+    set(section, option, value)
+        Set the given option.
+
+    write(fp, space_around_delimiters=True)
+        Write the configuration state in .ini format. If
+        `space_around_delimiters' is True (the default), delimiters
+        between keys and values are surrounded by spaces.
+"""
+
+from __future__ import with_statement
+from collections import MutableMapping
+from io import open
+try:
+    from collections import OrderedDict as _default_dict
+except ImportError:
+    from ordereddict import OrderedDict as _default_dict
+import functools
+import io
+import itertools
+import re
+import sys
+import warnings
+
+from configparser_helpers import _ChainMap
+
+__all__ = [u"NoSectionError", u"DuplicateOptionError", u"DuplicateSectionError",
+           u"NoOptionError", u"InterpolationError", u"InterpolationDepthError",
+           u"InterpolationSyntaxError", u"ParsingError",
+           u"MissingSectionHeaderError",
+           u"ConfigParser", u"SafeConfigParser", u"RawConfigParser",
+           u"DEFAULTSECT", u"MAX_INTERPOLATION_DEPTH"]
+
+DEFAULTSECT = u"DEFAULT"
+
+MAX_INTERPOLATION_DEPTH = 10
+
+
+
+# exception classes
+class Error(Exception):
+    u"""Base class for ConfigParser exceptions."""
+
+    def _get_message(self):
+        u"""Getter for 'message'; needed only to override deprecation in
+        BaseException.
+        """
+        return self.__message
+
+    def _set_message(self, value):
+        u"""Setter for 'message'; needed only to override deprecation in
+        BaseException.
+        """
+        self.__message = value
+
+    # BaseException.message has been deprecated since Python 2.6.  To prevent
+    # DeprecationWarning from popping up over this pre-existing attribute, use
+    # a new property that takes lookup precedence.
+    message = property(_get_message, _set_message)
+
+    def __init__(self, msg=u''):
+        self.message = msg
+        Exception.__init__(self, msg)
+
+    def __repr__(self):
+        return self.message
+
+    __str__ = __repr__
+
+
+class NoSectionError(Error):
+    u"""Raised when no section matches a requested option."""
+
+    def __init__(self, section):
+        Error.__init__(self, u'No section: %r' % (section,))
+        self.section = section
+        self.args = (section, )
+
+
+class DuplicateSectionError(Error):
+    u"""Raised when a section is repeated in an input source.
+
+    Possible repetitions that raise this exception are: multiple creation
+    using the API or in strict parsers when a section is found more than once
+    in a single input file, string or dictionary.
+    """
+
+    def __init__(self, section, source=None, lineno=None):
+        msg = [repr(section), u" already exists"]
+        if source is not None:
+            message = [u"While reading from ", source]
+            if lineno is not None:
+                message.append(u" [line {0:2d}]".format(lineno))
+            message.append(u": section ")
+            message.extend(msg)
+            msg = message
+        else:
+            msg.insert(0, u"Section ")
+        Error.__init__(self, u"".join(msg))
+        self.section = section
+        self.source = source
+        self.lineno = lineno
+        self.args = (section, source, lineno)
+
+
+class DuplicateOptionError(Error):
+    u"""Raised by strict parsers when an option is repeated in an input source.
+
+    Current implementation raises this exception only when an option is found
+    more than once in a single file, string or dictionary.
+    """
+
+    def __init__(self, section, option, source=None, lineno=None):
+        msg = [repr(option), u" in section ", repr(section),
+               u" already exists"]
+        if source is not None:
+            message = [u"While reading from ", source]
+            if lineno is not None:
+                message.append(u" [line {0:2d}]".format(lineno))
+            message.append(u": option ")
+            message.extend(msg)
+            msg = message
+        else:
+            msg.insert(0, u"Option ")
+        Error.__init__(self, u"".join(msg))
+        self.section = section
+        self.option = option
+        self.source = source
+        self.lineno = lineno
+        self.args = (section, option, source, lineno)
+
+
+class NoOptionError(Error):
+    u"""A requested option was not found."""
+
+    def __init__(self, option, section):
+        Error.__init__(self, u"No option %r in section: %r" %
+                       (option, section))
+        self.option = option
+        self.section = section
+        self.args = (option, section)
+
+
+class InterpolationError(Error):
+    u"""Base class for interpolation-related exceptions."""
+
+    def __init__(self, option, section, msg):
+        Error.__init__(self, msg)
+        self.option = option
+        self.section = section
+        self.args = (option, section, msg)
+
+
+class InterpolationMissingOptionError(InterpolationError):
+    u"""A string substitution required a setting which was not available."""
+
+    def __init__(self, option, section, rawval, reference):
+        msg = (u"Bad value substitution:\n"
+               u"\tsection: [%s]\n"
+               u"\toption : %s\n"
+               u"\tkey    : %s\n"
+               u"\trawval : %s\n"
+               % (section, option, reference, rawval))
+        InterpolationError.__init__(self, option, section, msg)
+        self.reference = reference
+        self.args = (option, section, rawval, reference)
+
+
+class InterpolationSyntaxError(InterpolationError):
+    u"""Raised when the source text contains invalid syntax.
+
+    Current implementation raises this exception when the source text into
+    which substitutions are made does not conform to the required syntax.
+    """
+
+
+class InterpolationDepthError(InterpolationError):
+    u"""Raised when substitutions are nested too deeply."""
+
+    def __init__(self, option, section, rawval):
+        msg = (u"Value interpolation too deeply recursive:\n"
+               u"\tsection: [%s]\n"
+               u"\toption : %s\n"
+               u"\trawval : %s\n"
+               % (section, option, rawval))
+        InterpolationError.__init__(self, option, section, msg)
+        self.args = (option, section, rawval)
+
+
+class ParsingError(Error):
+    u"""Raised when a configuration file does not follow legal syntax."""
+
+    def __init__(self, source=None, filename=None):
+        # Exactly one of `source'/`filename' arguments has to be given.
+        # `filename' kept for compatibility.
+        if filename and source:
+            raise ValueError(u"Cannot specify both `filename' and `source'. "
+                             u"Use `source'.")
+        elif not filename and not source:
+            raise ValueError(u"Required argument `source' not given.")
+        elif filename:
+            source = filename
+        Error.__init__(self, u'Source contains parsing errors: %s' % source)
+        self.source = source
+        self.errors = []
+        self.args = (source, )
+
+    @property
+    def filename(self):
+        u"""Deprecated, use `source'."""
+        warnings.warn(
+            u"The 'filename' attribute will be removed in future versions.  "
+            u"Use 'source' instead.",
+            DeprecationWarning, stacklevel=2
+        )
+        return self.source
+
+    @filename.setter
+    def filename(self, value):
+        u"""Deprecated, user `source'."""
+        warnings.warn(
+            u"The 'filename' attribute will be removed in future versions.  "
+            u"Use 'source' instead.",
+            DeprecationWarning, stacklevel=2
+        )
+        self.source = value
+
+    def append(self, lineno, line):
+        self.errors.append((lineno, line))
+        self.message += u'\n\t[line %2d]: %s' % (lineno, line)
+
+
+class MissingSectionHeaderError(ParsingError):
+    u"""Raised when a key-value pair is found before any section header."""
+
+    def __init__(self, filename, lineno, line):
+        Error.__init__(
+            self,
+            u'File contains no section headers.\nfile: %s, line: %d\n%r' %
+            (filename, lineno, line))
+        self.source = filename
+        self.lineno = lineno
+        self.line = line
+        self.args = (filename, lineno, line)
+
+
+# Used in parser getters to indicate the default behaviour when a specific
+# option is not found it to raise an exception. Created to enable `None' as
+# a valid fallback value.
+_UNSET = object()
+
+
+class Interpolation(object):
+    u"""Dummy interpolation that passes the value through with no changes."""
+
+    def before_get(self, parser, section, option, value, defaults):
+        return value
+
+    def before_set(self, parser, section, option, value):
+        return value
+
+    def before_read(self, parser, section, option, value):
+        return value
+
+    def before_write(self, parser, section, option, value):
+        return value
+
+
+class BasicInterpolation(Interpolation):
+    u"""Interpolation as implemented in the classic ConfigParser.
+
+    The option values can contain format strings which refer to other values in
+    the same section, or values in the special default section.
+
+    For example:
+
+        something: %(dir)s/whatever
+
+    would resolve the "%(dir)s" to the value of dir.  All reference
+    expansions are done late, on demand. If a user needs to use a bare % in
+    a configuration file, she can escape it by writing %%. Other other % usage
+    is considered a user error and raises `InterpolationSyntaxError'."""
+
+    _KEYCRE = re.compile(ur"%\(([^)]+)\)s")
+
+    def before_get(self, parser, section, option, value, defaults):
+        L = []
+        self._interpolate_some(parser, option, L, value, section, defaults, 1)
+        return u''.join(L)
+
+    def before_set(self, parser, section, option, value):
+        tmp_value = value.replace(u'%%', u'') # escaped percent signs
+        tmp_value = self._KEYCRE.sub(u'', tmp_value) # valid syntax
+        if u'%' in tmp_value:
+            raise ValueError(u"invalid interpolation syntax in %r at "
+                             u"position %d" % (value, tmp_value.find(u'%')))
+        return value
+
+    def _interpolate_some(self, parser, option, accum, rest, section, map,
+                          depth):
+        if depth > MAX_INTERPOLATION_DEPTH:
+            raise InterpolationDepthError(option, section, rest)
+        while rest:
+            p = rest.find(u"%")
+            if p < 0:
+                accum.append(rest)
+                return
+            if p > 0:
+                accum.append(rest[:p])
+                rest = rest[p:]
+            # p is no longer used
+            c = rest[1:2]
+            if c == u"%":
+                accum.append(u"%")
+                rest = rest[2:]
+            elif c == u"(":
+                m = self._KEYCRE.match(rest)
+                if m is None:
+                    raise InterpolationSyntaxError(option, section,
+                        u"bad interpolation variable reference %r" % rest)
+                var = parser.optionxform(m.group(1))
+                rest = rest[m.end():]
+                try:
+                    v = map[var]
+                except KeyError:
+                    raise InterpolationMissingOptionError(
+                        option, section, rest, var)
+                if u"%" in v:
+                    self._interpolate_some(parser, option, accum, v,
+                                           section, map, depth + 1)
+                else:
+                    accum.append(v)
+            else:
+                raise InterpolationSyntaxError(
+                    option, section,
+                    u"'%%' must be followed by '%%' or '(', "
+                    u"found: %r" % (rest,))
+
+
+class ExtendedInterpolation(Interpolation):
+    u"""Advanced variant of interpolation, supports the syntax used by
+    `zc.buildout'. Enables interpolation between sections."""
+
+    _KEYCRE = re.compile(ur"\$\{([^}]+)\}")
+
+    def before_get(self, parser, section, option, value, defaults):
+        L = []
+        self._interpolate_some(parser, option, L, value, section, defaults, 1)
+        return u''.join(L)
+
+    def before_set(self, parser, section, option, value):
+        tmp_value = value.replace(u'$$', u'') # escaped dollar signs
+        tmp_value = self._KEYCRE.sub(u'', tmp_value) # valid syntax
+        if u'$' in tmp_value:
+            raise ValueError(u"invalid interpolation syntax in %r at "
+                             u"position %d" % (value, tmp_value.find(u'%')))
+        return value
+
+    def _interpolate_some(self, parser, option, accum, rest, section, map,
+                          depth):
+        if depth > MAX_INTERPOLATION_DEPTH:
+            raise InterpolationDepthError(option, section, rest)
+        while rest:
+            p = rest.find(u"$")
+            if p < 0:
+                accum.append(rest)
+                return
+            if p > 0:
+                accum.append(rest[:p])
+                rest = rest[p:]
+            # p is no longer used
+            c = rest[1:2]
+            if c == u"$":
+                accum.append(u"$")
+                rest = rest[2:]
+            elif c == u"{":
+                m = self._KEYCRE.match(rest)
+                if m is None:
+                    raise InterpolationSyntaxError(option, section,
+                        u"bad interpolation variable reference %r" % rest)
+                path = m.group(1).split(u':')
+                rest = rest[m.end():]
+                sect = section
+                opt = option
+                try:
+                    if len(path) == 1:
+                        opt = parser.optionxform(path[0])
+                        v = map[opt]
+                    elif len(path) == 2:
+                        sect = path[0]
+                        opt = parser.optionxform(path[1])
+                        v = parser.get(sect, opt, raw=True)
+                    else:
+                        raise InterpolationSyntaxError(
+                            option, section,
+                            u"More than one ':' found: %r" % (rest,))
+                except (KeyError, NoSectionError, NoOptionError):
+                    raise InterpolationMissingOptionError(
+                        option, section, rest, u":".join(path))
+                if u"$" in v:
+                    self._interpolate_some(parser, opt, accum, v, sect,
+                                           dict(parser.items(sect, raw=True)),
+                                           depth + 1)
+                else:
+                    accum.append(v)
+            else:
+                raise InterpolationSyntaxError(
+                    option, section,
+                    u"'$' must be followed by '$' or '{', "
+                    u"found: %r" % (rest,))
+
+
+class LegacyInterpolation(Interpolation):
+    u"""Deprecated interpolation used in old versions of ConfigParser.
+    Use BasicInterpolation or ExtendedInterpolation instead."""
+
+    _KEYCRE = re.compile(ur"%\(([^)]*)\)s|.")
+
+    def before_get(self, parser, section, option, value, vars):
+        rawval = value
+        depth = MAX_INTERPOLATION_DEPTH
+        while depth:                    # Loop through this until it's done
+            depth -= 1
+            if value and u"%(" in value:
+                replace = functools.partial(self._interpolation_replace,
+                                            parser=parser)
+                value = self._KEYCRE.sub(replace, value)
+                try:
+                    value = value % vars
+                except KeyError, e:
+                    raise InterpolationMissingOptionError(
+                        option, section, rawval, e.args[0])
+            else:
+                break
+        if value and u"%(" in value:
+            raise InterpolationDepthError(option, section, rawval)
+        return value
+
+    def before_set(self, parser, section, option, value):
+        return value
+
+    @staticmethod
+    def _interpolation_replace(match, parser):
+        s = match.group(1)
+        if s is None:
+            return match.group()
+        else:
+            return u"%%(%s)s" % parser.optionxform(s)
+
+
+class RawConfigParser(MutableMapping):
+    u"""ConfigParser that does not do interpolation."""
+
+    # Regular expressions for parsing section headers and options
+    _SECT_TMPL = ur"""
+        \[                                 # [
+        (?P<header>[^]]+)                  # very permissive!
+        \]                                 # ]
+        """
+    _OPT_TMPL = ur"""
+        (?P<option>.*?)                    # very permissive!
+        \s*(?P<vi>{delim})\s*              # any number of space/tab,
+                                           # followed by any of the
+                                           # allowed delimiters,
+                                           # followed by any space/tab
+        (?P<value>.*)$                     # everything up to eol
+        """
+    _OPT_NV_TMPL = ur"""
+        (?P<option>.*?)                    # very permissive!
+        \s*(?:                             # any number of space/tab,
+        (?P<vi>{delim})\s*                 # optionally followed by
+                                           # any of the allowed
+                                           # delimiters, followed by any
+                                           # space/tab
+        (?P<value>.*))?$                   # everything up to eol
+        """
+    # Interpolation algorithm to be used if the user does not specify another
+    _DEFAULT_INTERPOLATION = Interpolation()
+    # Compiled regular expression for matching sections
+    SECTCRE = re.compile(_SECT_TMPL, re.VERBOSE)
+    # Compiled regular expression for matching options with typical separators
+    OPTCRE = re.compile(_OPT_TMPL.format(delim=u"=|:"), re.VERBOSE)
+    # Compiled regular expression for matching options with optional values
+    # delimited using typical separators
+    OPTCRE_NV = re.compile(_OPT_NV_TMPL.format(delim=u"=|:"), re.VERBOSE)
+    # Compiled regular expression for matching leading whitespace in a line
+    NONSPACECRE = re.compile(ur"\S")
+    # Possible boolean values in the configuration.
+    BOOLEAN_STATES = {u'1': True, u'yes': True, u'true': True, u'on': True,
+                      u'0': False, u'no': False, u'false': False, u'off': False}
+
+    def __init__(self, defaults=None, dict_type=_default_dict,
+                 allow_no_value=False, **_3to2kwargs):
+
+        if 'interpolation' in _3to2kwargs: interpolation = _3to2kwargs['interpolation']; del _3to2kwargs['interpolation']
+        else: interpolation = _UNSET
+        if 'default_section' in _3to2kwargs: default_section = _3to2kwargs['default_section']; del _3to2kwargs['default_section']
+        else: default_section = DEFAULTSECT
+        if 'empty_lines_in_values' in _3to2kwargs: empty_lines_in_values = _3to2kwargs['empty_lines_in_values']; del _3to2kwargs['empty_lines_in_values']
+        else: empty_lines_in_values = True
+        if 'strict' in _3to2kwargs: strict = _3to2kwargs['strict']; del _3to2kwargs['strict']
+        else: strict = True
+        if 'inline_comment_prefixes' in _3to2kwargs: inline_comment_prefixes = _3to2kwargs['inline_comment_prefixes']; del _3to2kwargs['inline_comment_prefixes']
+        else: inline_comment_prefixes = None
+        if 'comment_prefixes' in _3to2kwargs: comment_prefixes = _3to2kwargs['comment_prefixes']; del _3to2kwargs['comment_prefixes']
+        else: comment_prefixes = (u'#', u';')
+        if 'delimiters' in _3to2kwargs: delimiters = _3to2kwargs['delimiters']; del _3to2kwargs['delimiters']
+        else: delimiters = (u'=', u':')
+        self._dict = dict_type
+        self._sections = self._dict()
+        self._defaults = self._dict()
+        self._proxies = self._dict()
+        self._proxies[default_section] = SectionProxy(self, default_section)
+        if defaults:
+            for key, value in defaults.items():
+                self._defaults[self.optionxform(key)] = value
+        self._delimiters = tuple(delimiters)
+        if delimiters == (u'=', u':'):
+            self._optcre = self.OPTCRE_NV if allow_no_value else self.OPTCRE
+        else:
+            d = u"|".join(re.escape(d) for d in delimiters)
+            if allow_no_value:
+                self._optcre = re.compile(self._OPT_NV_TMPL.format(delim=d),
+                                          re.VERBOSE)
+            else:
+                self._optcre = re.compile(self._OPT_TMPL.format(delim=d),
+                                          re.VERBOSE)
+        self._comment_prefixes = tuple(comment_prefixes or ())
+        self._inline_comment_prefixes = tuple(inline_comment_prefixes or ())
+        self._strict = strict
+        self._allow_no_value = allow_no_value
+        self._empty_lines_in_values = empty_lines_in_values
+        self.default_section=default_section
+        self._interpolation = interpolation
+        if self._interpolation is _UNSET:
+            self._interpolation = self._DEFAULT_INTERPOLATION
+        if self._interpolation is None:
+            self._interpolation = Interpolation()
+
+    def defaults(self):
+        return self._defaults
+
+    def sections(self):
+        u"""Return a list of section names, excluding [DEFAULT]"""
+        # self._sections will never have [DEFAULT] in it
+        return list(self._sections.keys())
+
+    def add_section(self, section):
+        u"""Create a new section in the configuration.
+
+        Raise DuplicateSectionError if a section by the specified name
+        already exists. Raise ValueError if name is DEFAULT.
+        """
+        if section == self.default_section:
+            raise ValueError(u'Invalid section name: %r' % section)
+
+        if section in self._sections:
+            raise DuplicateSectionError(section)
+        self._sections[section] = self._dict()
+        self._proxies[section] = SectionProxy(self, section)
+
+    def has_section(self, section):
+        u"""Indicate whether the named section is present in the configuration.
+
+        The DEFAULT section is not acknowledged.
+        """
+        return section in self._sections
+
+    def options(self, section):
+        u"""Return a list of option names for the given section name."""
+        try:
+            opts = self._sections[section].copy()
+        except KeyError:
+            raise NoSectionError(section)
+        opts.update(self._defaults)
+        return list(opts.keys())
+
+    def read(self, filenames, encoding=None):
+        u"""Read and parse a filename or a list of filenames.
+
+        Files that cannot be opened are silently ignored; this is
+        designed so that you can specify a list of potential
+        configuration file locations (e.g. current directory, user's
+        home directory, systemwide directory), and all existing
+        configuration files in the list will be read.  A single
+        filename may also be given.
+
+        Return list of successfully read files.
+        """
+        if isinstance(filenames, unicode):
+            filenames = [filenames]
+        read_ok = []
+        for filename in filenames:
+            try:
+                with open(filename, encoding=encoding) as fp:
+                    self._read(fp, filename)
+            except IOError:
+                continue
+            read_ok.append(filename)
+        return read_ok
+
+    def read_file(self, f, source=None):
+        u"""Like read() but the argument must be a file-like object.
+
+        The `f' argument must be iterable, returning one line at a time.
+        Optional second argument is the `source' specifying the name of the
+        file being read. If not given, it is taken from f.name. If `f' has no
+        `name' attribute, `<???>' is used.
+        """
+        if source is None:
+            try:
+                source = f.name
+            except AttributeError:
+                source = u'<???>'
+        self._read(f, source)
+
+    def read_string(self, string, source=u'<string>'):
+        u"""Read configuration from a given string."""
+        sfile = io.StringIO(string)
+        self.read_file(sfile, source)
+
+    def read_dict(self, dictionary, source=u'<dict>'):
+        u"""Read configuration from a dictionary.
+
+        Keys are section names, values are dictionaries with keys and values
+        that should be present in the section. If the used dictionary type
+        preserves order, sections and their keys will be added in order.
+
+        All types held in the dictionary are converted to strings during
+        reading, including section names, option names and keys.
+
+        Optional second argument is the `source' specifying the name of the
+        dictionary being read.
+        """
+        elements_added = set()
+        for section, keys in dictionary.items():
+            section = unicode(section)
+            try:
+                self.add_section(section)
+            except (DuplicateSectionError, ValueError):
+                if self._strict and section in elements_added:
+                    raise
+            elements_added.add(section)
+            for key, value in keys.items():
+                key = self.optionxform(unicode(key))
+                if value is not None:
+                    value = unicode(value)
+                if self._strict and (section, key) in elements_added:
+                    raise DuplicateOptionError(section, key, source)
+                elements_added.add((section, key))
+                self.set(section, key, value)
+
+    def readfp(self, fp, filename=None):
+        u"""Deprecated, use read_file instead."""
+        warnings.warn(
+            u"This method will be removed in future versions.  "
+            u"Use 'parser.read_file()' instead.",
+            DeprecationWarning, stacklevel=2
+        )
+        self.read_file(fp, source=filename)
+
+    def get(self, section, option, **_3to2kwargs):
+        if 'fallback' in _3to2kwargs: fallback = _3to2kwargs['fallback']; del _3to2kwargs['fallback']
+        else: fallback = _UNSET
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        u"""Get an option value for a given section.
+
+        If `vars' is provided, it must be a dictionary. The option is looked up
+        in `vars' (if provided), `section', and in `DEFAULTSECT' in that order.
+        If the key is not found and `fallback' is provided, it is used as
+        a fallback value. `None' can be provided as a `fallback' value.
+
+        If interpolation is enabled and the optional argument `raw' is False,
+        all interpolations are expanded in the return values.
+
+        Arguments `raw', `vars', and `fallback' are keyword only.
+
+        The section DEFAULT is special.
+        """
+        try:
+            d = self._unify_values(section, vars)
+        except NoSectionError:
+            if fallback is _UNSET:
+                raise
+            else:
+                return fallback
+        option = self.optionxform(option)
+        try:
+            value = d[option]
+        except KeyError:
+            if fallback is _UNSET:
+                raise NoOptionError(option, section)
+            else:
+                return fallback
+
+        if raw or value is None:
+            return value
+        else:
+            return self._interpolation.before_get(self, section, option, value,
+                                                  d)
+
+    def _get(self, section, conv, option, **kwargs):
+        return conv(self.get(section, option, **kwargs))
+
+    def getint(self, section, option, **_3to2kwargs):
+        if 'fallback' in _3to2kwargs: fallback = _3to2kwargs['fallback']; del _3to2kwargs['fallback']
+        else: fallback = _UNSET
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        try:
+            return self._get(section, int, option, raw=raw, vars=vars)
+        except (NoSectionError, NoOptionError):
+            if fallback is _UNSET:
+                raise
+            else:
+                return fallback
+
+    def getfloat(self, section, option, **_3to2kwargs):
+        if 'fallback' in _3to2kwargs: fallback = _3to2kwargs['fallback']; del _3to2kwargs['fallback']
+        else: fallback = _UNSET
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        try:
+            return self._get(section, float, option, raw=raw, vars=vars)
+        except (NoSectionError, NoOptionError):
+            if fallback is _UNSET:
+                raise
+            else:
+                return fallback
+
+    def getboolean(self, section, option, **_3to2kwargs):
+        if 'fallback' in _3to2kwargs: fallback = _3to2kwargs['fallback']; del _3to2kwargs['fallback']
+        else: fallback = _UNSET
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        try:
+            return self._get(section, self._convert_to_boolean, option,
+                             raw=raw, vars=vars)
+        except (NoSectionError, NoOptionError):
+            if fallback is _UNSET:
+                raise
+            else:
+                return fallback
+
+    def items(self, section=_UNSET, raw=False, vars=None):
+        u"""Return a list of (name, value) tuples for each option in a section.
+
+        All % interpolations are expanded in the return values, based on the
+        defaults passed into the constructor, unless the optional argument
+        `raw' is true.  Additional substitutions may be provided using the
+        `vars' argument, which must be a dictionary whose contents overrides
+        any pre-existing defaults.
+
+        The section DEFAULT is special.
+        """
+        if section is _UNSET:
+            return super(RawConfigParser, self).items()
+        d = self._defaults.copy()
+        try:
+            d.update(self._sections[section])
+        except KeyError:
+            if section != self.default_section:
+                raise NoSectionError(section)
+        # Update with the entry specific variables
+        if vars:
+            for key, value in vars.items():
+                d[self.optionxform(key)] = value
+        value_getter = lambda option: self._interpolation.before_get(self,
+            section, option, d[option], d)
+        if raw:
+            value_getter = lambda option: d[option]
+        return [(option, value_getter(option)) for option in d.keys()]
+
+    def optionxform(self, optionstr):
+        return optionstr.lower()
+
+    def has_option(self, section, option):
+        u"""Check for the existence of a given option in a given section.
+        If the specified `section' is None or an empty string, DEFAULT is
+        assumed. If the specified `section' does not exist, returns False."""
+        if not section or section == self.default_section:
+            option = self.optionxform(option)
+            return option in self._defaults
+        elif section not in self._sections:
+            return False
+        else:
+            option = self.optionxform(option)
+            return (option in self._sections[section]
+                    or option in self._defaults)
+
+    def set(self, section, option, value=None):
+        u"""Set an option."""
+        if value:
+            value = self._interpolation.before_set(self, section, option,
+                                                   value)
+        if not section or section == self.default_section:
+            sectdict = self._defaults
+        else:
+            try:
+                sectdict = self._sections[section]
+            except KeyError:
+                raise NoSectionError(section)
+        sectdict[self.optionxform(option)] = value
+
+    def write(self, fp, space_around_delimiters=True):
+        u"""Write an .ini-format representation of the configuration state.
+
+        If `space_around_delimiters' is True (the default), delimiters
+        between keys and values are surrounded by spaces.
+        """
+        if space_around_delimiters:
+            d = u" {0} ".format(self._delimiters[0])
+        else:
+            d = self._delimiters[0]
+        if self._defaults:
+            self._write_section(fp, self.default_section,
+                                    self._defaults.items(), d)
+        for section in self._sections:
+            self._write_section(fp, section,
+                                self._sections[section].items(), d)
+
+    def _write_section(self, fp, section_name, section_items, delimiter):
+        u"""Write a single section to the specified `fp'."""
+        fp.write(u"[{0}]\n".format(section_name))
+        for key, value in section_items:
+            value = self._interpolation.before_write(self, section_name, key,
+                                                     value)
+            if value is not None or not self._allow_no_value:
+                value = delimiter + unicode(value).replace(u'\n', u'\n\t')
+            else:
+                value = u""
+            fp.write(u"{0}{1}\n".format(key, value))
+        fp.write(u"\n")
+
+    def remove_option(self, section, option):
+        u"""Remove an option."""
+        if not section or section == self.default_section:
+            sectdict = self._defaults
+        else:
+            try:
+                sectdict = self._sections[section]
+            except KeyError:
+                raise NoSectionError(section)
+        option = self.optionxform(option)
+        existed = option in sectdict
+        if existed:
+            del sectdict[option]
+        return existed
+
+    def remove_section(self, section):
+        u"""Remove a file section."""
+        existed = section in self._sections
+        if existed:
+            del self._sections[section]
+            del self._proxies[section]
+        return existed
+
+    def __getitem__(self, key):
+        if key != self.default_section and not self.has_section(key):
+            raise KeyError(key)
+        return self._proxies[key]
+
+    def __setitem__(self, key, value):
+        # To conform with the mapping protocol, overwrites existing values in
+        # the section.
+
+        # XXX this is not atomic if read_dict fails at any point. Then again,
+        # no update method in configparser is atomic in this implementation.
+        self.remove_section(key)
+        self.read_dict({key: value})
+
+    def __delitem__(self, key):
+        if key == self.default_section:
+            raise ValueError(u"Cannot remove the default section.")
+        if not self.has_section(key):
+            raise KeyError(key)
+        self.remove_section(key)
+
+    def __contains__(self, key):
+        return key == self.default_section or self.has_section(key)
+
+    def __len__(self):
+        return len(self._sections) + 1 # the default section
+
+    def __iter__(self):
+        # XXX does it break when underlying container state changed?
+        return itertools.chain((self.default_section,), self._sections.keys())
+
+    def _read(self, fp, fpname):
+        u"""Parse a sectioned configuration file.
+
+        Each section in a configuration file contains a header, indicated by
+        a name in square brackets (`[]'), plus key/value options, indicated by
+        `name' and `value' delimited with a specific substring (`=' or `:' by
+        default).
+
+        Values can span multiple lines, as long as they are indented deeper
+        than the first line of the value. Depending on the parser's mode, blank
+        lines may be treated as parts of multiline values or ignored.
+
+        Configuration files may include comments, prefixed by specific
+        characters (`#' and `;' by default). Comments may appear on their own
+        in an otherwise empty line or may be entered in lines holding values or
+        section names.
+        """
+        elements_added = set()
+        cursect = None                        # None, or a dictionary
+        sectname = None
+        optname = None
+        lineno = 0
+        indent_level = 0
+        e = None                              # None, or an exception
+        for lineno, line in enumerate(fp, start=1):
+            comment_start = None
+            # strip inline comments
+            for prefix in self._inline_comment_prefixes:
+                index = line.find(prefix)
+                if index == 0 or (index > 0 and line[index-1].isspace()):
+                    comment_start = index
+                    break
+            # strip full line comments
+            for prefix in self._comment_prefixes:
+                if line.strip().startswith(prefix):
+                    comment_start = 0
+                    break
+            value = line[:comment_start].strip()
+            if not value:
+                if self._empty_lines_in_values:
+                    # add empty line to the value, but only if there was no
+                    # comment on the line
+                    if (comment_start is None and
+                        cursect is not None and
+                        optname and
+                        cursect[optname] is not None):
+                        cursect[optname].append(u'') # newlines added at join
+                else:
+                    # empty line marks end of value
+                    indent_level = sys.maxsize
+                continue
+            # continuation line?
+            first_nonspace = self.NONSPACECRE.search(line)
+            cur_indent_level = first_nonspace.start() if first_nonspace else 0
+            if (cursect is not None and optname and
+                cur_indent_level > indent_level):
+                cursect[optname].append(value)
+            # a section header or option header?
+            else:
+                indent_level = cur_indent_level
+                # is it a section header?
+                mo = self.SECTCRE.match(value)
+                if mo:
+                    sectname = mo.group(u'header')
+                    if sectname in self._sections:
+                        if self._strict and sectname in elements_added:
+                            raise DuplicateSectionError(sectname, fpname,
+                                                        lineno)
+                        cursect = self._sections[sectname]
+                        elements_added.add(sectname)
+                    elif sectname == self.default_section:
+                        cursect = self._defaults
+                    else:
+                        cursect = self._dict()
+                        self._sections[sectname] = cursect
+                        self._proxies[sectname] = SectionProxy(self, sectname)
+                        elements_added.add(sectname)
+                    # So sections can't start with a continuation line
+                    optname = None
+                # no section header in the file?
+                elif cursect is None:
+                    raise MissingSectionHeaderError(fpname, lineno, line)
+                # an option line?
+                else:
+                    mo = self._optcre.match(value)
+                    if mo:
+                        optname, vi, optval = mo.group(u'option', u'vi', u'value')
+                        if not optname:
+                            e = self._handle_error(e, fpname, lineno, line)
+                        optname = self.optionxform(optname.rstrip())
+                        if (self._strict and
+                            (sectname, optname) in elements_added):
+                            raise DuplicateOptionError(sectname, optname,
+                                                       fpname, lineno)
+                        elements_added.add((sectname, optname))
+                        # This check is fine because the OPTCRE cannot
+                        # match if it would set optval to None
+                        if optval is not None:
+                            optval = optval.strip()
+                            cursect[optname] = [optval]
+                        else:
+                            # valueless option handling
+                            cursect[optname] = None
+                    else:
+                        # a non-fatal parsing error occurred. set up the
+                        # exception but keep going. the exception will be
+                        # raised at the end of the file and will contain a
+                        # list of all bogus lines
+                        e = self._handle_error(e, fpname, lineno, line)
+        # if any parsing errors occurred, raise an exception
+        if e:
+            raise e
+        self._join_multiline_values()
+
+    def _join_multiline_values(self):
+        defaults = self.default_section, self._defaults
+        all_sections = itertools.chain((defaults,),
+                                       self._sections.items())
+        for section, options in all_sections:
+            for name, val in options.items():
+                if isinstance(val, list):
+                    val = u'\n'.join(val).rstrip()
+                options[name] = self._interpolation.before_read(self,
+                                                                section,
+                                                                name, val)
+
+    def _handle_error(self, exc, fpname, lineno, line):
+        if not exc:
+            exc = ParsingError(fpname)
+        exc.append(lineno, repr(line))
+        return exc
+
+    def _unify_values(self, section, vars):
+        u"""Create a sequence of lookups with 'vars' taking priority over
+        the 'section' which takes priority over the DEFAULTSECT.
+
+        """
+        sectiondict = {}
+        try:
+            sectiondict = self._sections[section]
+        except KeyError:
+            if section != self.default_section:
+                raise NoSectionError(section)
+        # Update with the entry specific variables
+        vardict = {}
+        if vars:
+            for key, value in vars.items():
+                if value is not None:
+                    value = unicode(value)
+                vardict[self.optionxform(key)] = value
+        return _ChainMap(vardict, sectiondict, self._defaults)
+
+    def _convert_to_boolean(self, value):
+        u"""Return a boolean value translating from other types if necessary.
+        """
+        if value.lower() not in self.BOOLEAN_STATES:
+            raise ValueError(u'Not a boolean: %s' % value)
+        return self.BOOLEAN_STATES[value.lower()]
+
+    def _validate_value_types(self, **_3to2kwargs):
+        if 'value' in _3to2kwargs: value = _3to2kwargs['value']; del _3to2kwargs['value']
+        else: value = u""
+        if 'option' in _3to2kwargs: option = _3to2kwargs['option']; del _3to2kwargs['option']
+        else: option = u""
+        if 'section' in _3to2kwargs: section = _3to2kwargs['section']; del _3to2kwargs['section']
+        else: section = u""
+        u"""Raises a TypeError for non-string values.
+
+        The only legal non-string value if we allow valueless
+        options is None, so we need to check if the value is a
+        string if:
+        - we do not allow valueless options, or
+        - we allow valueless options but the value is not None
+
+        For compatibility reasons this method is not used in classic set()
+        for RawConfigParsers. It is invoked in every case for mapping protocol
+        access and in ConfigParser.set().
+        """
+        if not isinstance(section, basestring):
+            raise TypeError(u"section names must be strings")
+        if not isinstance(option, basestring):
+            raise TypeError(u"option keys must be strings")
+        if not self._allow_no_value or value:
+            if not isinstance(value, basestring):
+                raise TypeError(u"option values must be strings")
+        return (unicode(section), unicode(option), (value if value is None
+            else unicode(value)))
+
+
+class ConfigParser(RawConfigParser):
+    u"""ConfigParser implementing interpolation."""
+
+    _DEFAULT_INTERPOLATION = BasicInterpolation()
+
+    def set(self, section, option, value=None):
+        u"""Set an option.  Extends RawConfigParser.set by validating type and
+        interpolation syntax on the value."""
+        _, option, value = self._validate_value_types(option=option, value=value)
+        super(ConfigParser, self).set(section, option, value)
+
+    def add_section(self, section):
+        u"""Create a new section in the configuration.  Extends
+        RawConfigParser.add_section by validating if the section name is
+        a string."""
+        section, _, _ = self._validate_value_types(section=section)
+        super(ConfigParser, self).add_section(section)
+
+
+class SafeConfigParser(ConfigParser):
+    u"""ConfigParser alias for backwards compatibility purposes."""
+
+    def __init__(self, *args, **kwargs):
+        super(SafeConfigParser, self).__init__(*args, **kwargs)
+        warnings.warn(
+            u"The SafeConfigParser class has been renamed to ConfigParser "
+            u"in Python 3.2. This alias will be removed in future versions."
+            u" Use ConfigParser directly instead.",
+            DeprecationWarning, stacklevel=2
+        )
+
+
+class SectionProxy(MutableMapping):
+    u"""A proxy for a single section from a parser."""
+
+    def __init__(self, parser, name):
+        u"""Creates a view on a section of the specified `name` in `parser`."""
+        self._parser = parser
+        self._name = name
+
+    def __repr__(self):
+        return u'<Section: {0}>'.format(self._name)
+
+    def __getitem__(self, key):
+        if not self._parser.has_option(self._name, key):
+            raise KeyError(key)
+        return self._parser.get(self._name, key)
+
+    def __setitem__(self, key, value):
+        _, key, value = self._parser._validate_value_types(option=key, value=value)
+        return self._parser.set(self._name, key, value)
+
+    def __delitem__(self, key):
+        if not (self._parser.has_option(self._name, key) and
+                self._parser.remove_option(self._name, key)):
+            raise KeyError(key)
+
+    def __contains__(self, key):
+        return self._parser.has_option(self._name, key)
+
+    def __len__(self):
+        return len(self._options())
+
+    def __iter__(self):
+        return self._options().__iter__()
+
+    def _options(self):
+        if self._name != self._parser.default_section:
+            return self._parser.options(self._name)
+        else:
+            return self._parser.defaults()
+
+    def get(self, option, fallback=None, **_3to2kwargs):
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        return self._parser.get(self._name, option, raw=raw, vars=vars,
+                                fallback=fallback)
+
+    def getint(self, option, fallback=None, **_3to2kwargs):
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        return self._parser.getint(self._name, option, raw=raw, vars=vars,
+                                   fallback=fallback)
+
+    def getfloat(self, option, fallback=None, **_3to2kwargs):
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        return self._parser.getfloat(self._name, option, raw=raw, vars=vars,
+                                     fallback=fallback)
+
+    def getboolean(self, option, fallback=None, **_3to2kwargs):
+        if 'vars' in _3to2kwargs: vars = _3to2kwargs['vars']; del _3to2kwargs['vars']
+        else: vars = None
+        if 'raw' in _3to2kwargs: raw = _3to2kwargs['raw']; del _3to2kwargs['raw']
+        else: raw = False
+        return self._parser.getboolean(self._name, option, raw=raw, vars=vars,
+                                       fallback=fallback)
+
+    @property
+    def parser(self):
+        # The parser object of the proxy is read-only.
+        return self._parser
+
+    @property
+    def name(self):
+        # The name of the section on a proxy is read-only.
+        return self._name
diff --git a/configparser_helpers.py b/configparser_helpers.py
new file mode 100644
index 0000000..470cd5f
--- /dev/null
+++ b/configparser_helpers.py
@@ -0,0 +1,134 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+from collections import MutableMapping
+try:
+    from thread import get_ident
+except ImportError:
+    try:
+        from _thread import get_ident
+    except ImportError:
+        from _dummy_thread import get_ident
+
+# from reprlib 3.2.1
+def recursive_repr(fillvalue=u'...'):
+    u'Decorator to make a repr function return fillvalue for a recursive call'
+
+    def decorating_function(user_function):
+        repr_running = set()
+
+        def wrapper(self):
+            key = id(self), get_ident()
+            if key in repr_running:
+                return fillvalue
+            repr_running.add(key)
+            try:
+                result = user_function(self)
+            finally:
+                repr_running.discard(key)
+            return result
+
+        # Can't use functools.wraps() here because of bootstrap issues
+        wrapper.__module__ = getattr(user_function, u'__module__')
+        wrapper.__doc__ = getattr(user_function, u'__doc__')
+        wrapper.__name__ = getattr(user_function, u'__name__')
+        wrapper.__annotations__ = getattr(user_function, u'__annotations__', {})
+        return wrapper
+
+    return decorating_function
+
+# from collections 3.2.1
+class _ChainMap(MutableMapping):
+    u''' A ChainMap groups multiple dicts (or other mappings) together
+    to create a single, updateable view.
+
+    The underlying mappings are stored in a list.  That list is public and can
+    accessed or updated using the *maps* attribute.  There is no other state.
+
+    Lookups search the underlying mappings successively until a key is found.
+    In contrast, writes, updates, and deletions only operate on the first
+    mapping.
+
+    '''
+
+    def __init__(self, *maps):
+        u'''Initialize a ChainMap by setting *maps* to the given mappings.
+        If no mappings are provided, a single empty dictionary is used.
+
+        '''
+        self.maps = list(maps) or [{}]          # always at least one map
+
+    def __missing__(self, key):
+        raise KeyError(key)
+
+    def __getitem__(self, key):
+        for mapping in self.maps:
+            try:
+                return mapping[key]             # can't use 'key in mapping' with defaultdict
+            except KeyError:
+                pass
+        return self.__missing__(key)            # support subclasses that define __missing__
+
+    def get(self, key, default=None):
+        return self[key] if key in self else default
+
+    def __len__(self):
+        return len(set().union(*self.maps))     # reuses stored hash values if possible
+
+    def __iter__(self):
+        return iter(set().union(*self.maps))
+
+    def __contains__(self, key):
+        return any(key in m for m in self.maps)
+
+    @recursive_repr()
+    def __repr__(self):
+        return u'{0.__class__.__name__}({1})'.format(
+            self, u', '.join(map(repr, self.maps)))
+
+    @classmethod
+    def fromkeys(cls, iterable, *args):
+        u'Create a ChainMap with a single dict created from the iterable.'
+        return cls(dict.fromkeys(iterable, *args))
+
+    def copy(self):
+        u'New ChainMap or subclass with a new copy of maps[0] and refs to maps[1:]'
+        return self.__class__(self.maps[0].copy(), *self.maps[1:])
+
+    __copy__ = copy
+
+    def new_child(self):                        # like Django's Context.push()
+        u'New ChainMap with a new dict followed by all previous maps.'
+        return self.__class__({}, *self.maps)
+
+    @property
+    def parents(self):                          # like Django's Context.pop()
+        u'New ChainMap from maps[1:].'
+        return self.__class__(*self.maps[1:])
+
+    def __setitem__(self, key, value):
+        self.maps[0][key] = value
+
+    def __delitem__(self, key):
+        try:
+            del self.maps[0][key]
+        except KeyError:
+            raise KeyError(u'Key not found in the first mapping: {!r}'.format(key))
+
+    def popitem(self):
+        u'Remove and return an item pair from maps[0]. Raise KeyError is maps[0] is empty.'
+        try:
+            return self.maps[0].popitem()
+        except KeyError:
+            raise KeyError(u'No keys found in the first mapping.')
+
+    def pop(self, key, *args):
+        u'Remove *key* from maps[0] and return its value. Raise KeyError if *key* not in maps[0].'
+        try:
+            return self.maps[0].pop(key, *args)
+        except KeyError:
+            raise KeyError(u'Key not found in the first mapping: {!r}'.format(key))
+
+    def clear(self):
+        u'Clear maps[0], leaving maps[1:] intact.'
+        self.maps[0].clear()
-- 
2.7.4