python模块：configparser

 """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, default_section='DEFAULT',
              interpolation=<unset>, converters=<unset>):
         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.
 
         When `default_section' is given, the name of the special section is
         named accordingly. By default it is called ``"DEFAULT"`` but this can
         be customized to point to any other valid section name. Its current
         value can be retrieved using the ``parser_instance.default_section``
         attribute and may be modified at runtime.
 
         When `interpolation` is given, it should be an Interpolation subclass
         instance. It will be used as the handler for option value
         pre-processing when using getters. RawConfigParser object s don't do
         any sort of interpolation, whereas ConfigParser uses an instance of
         BasicInterpolation. The library also provides a ``zc.buildbot``
         inspired ExtendedInterpolation implementation.
 
         When `converters` is given, it should be a dictionary where each key
         represents the name of a type converter and each value is a callable
         implementing the conversion from string to the desired datatype. Every
         converter gets its corresponding get*() method on the parser object and
         section proxies.
 
     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 (name, value) for
         each option in the section. Otherwise, return a list of tuples with
         (section_name, section_proxy) for each section, including DEFAULTSECT.
 
     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 collections.abc import MutableMapping
 from collections import OrderedDict as _default_dict, ChainMap as _ChainMap
 import functools
 import io
 import itertools
 import os
 import re
 import sys
 import warnings
 
 __all__ = ["NoSectionError", "DuplicateOptionError", "DuplicateSectionError",
            "NoOptionError", "InterpolationError", "InterpolationDepthError",
            "InterpolationMissingOptionError", "InterpolationSyntaxError",
            "ParsingError", "MissingSectionHeaderError",
            "ConfigParser", "SafeConfigParser", "RawConfigParser",
            "Interpolation", "BasicInterpolation",  "ExtendedInterpolation",
            "LegacyInterpolation", "SectionProxy", "ConverterMapping",
            "DEFAULTSECT", "MAX_INTERPOLATION_DEPTH"]
 
 DEFAULTSECT = "DEFAULT"
 
 MAX_INTERPOLATION_DEPTH = 10
 
 # exception classes
 class Error(Exception):
     """Base class for ConfigParser exceptions."""
 
     def __init__(self, msg=''):
         self.message = msg
         Exception.__init__(self, msg)
 
     def __repr__(self):
         return self.message
 
     __str__ = __repr__
 
 class NoSectionError(Error):
     """Raised when no section matches a requested option."""
 
     def __init__(self, section):
         Error.__init__(self, 'No section: %r' % (section,))
         self.section = section
         self.args = (section, )
 
 class DuplicateSectionError(Error):
     """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), " already exists"]
         if source is not None:
             message = ["While reading from ", repr(source)]
             if lineno is not None:
                 message.append(" [line {0:2d}]".format(lineno))
             message.append(": section ")
             message.extend(msg)
             msg = message
         else:
             msg.insert(0, "Section ")
         Error.__init__(self, "".join(msg))
         self.section = section
         self.source = source
         self.lineno = lineno
         self.args = (section, source, lineno)
 
 class DuplicateOptionError(Error):
     """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), " in section ", repr(section),
                " already exists"]
         if source is not None:
             message = ["While reading from ", repr(source)]
             if lineno is not None:
                 message.append(" [line {0:2d}]".format(lineno))
             message.append(": option ")
             message.extend(msg)
             msg = message
         else:
             msg.insert(0, "Option ")
         Error.__init__(self, "".join(msg))
         self.section = section
         self.option = option
         self.source = source
         self.lineno = lineno
         self.args = (section, option, source, lineno)
 
 class NoOptionError(Error):
     """A requested option was not found."""
 
     def __init__(self, option, section):
         Error.__init__(self, "No option %r in section: %r" %
                        (option, section))
         self.option = option
         self.section = section
         self.args = (option, section)
 
 class InterpolationError(Error):
     """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):
     """A string substitution required a setting which was not available."""
 
     def __init__(self, option, section, rawval, reference):
         msg = ("Bad value substitution: option {!r} in section {!r} contains "
                "an interpolation key {!r} which is not a valid option name. "
                "Raw value: {!r}".format(option, section, reference, rawval))
         InterpolationError.__init__(self, option, section, msg)
         self.reference = reference
         self.args = (option, section, rawval, reference)
 
 class InterpolationSyntaxError(InterpolationError):
     """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):
     """Raised when substitutions are nested too deeply."""
 
     def __init__(self, option, section, rawval):
         msg = ("Recursion limit exceeded in value substitution: option {!r} "
                "in section {!r} contains an interpolation key which "
                "cannot be substituted in {} steps. Raw value: {!r}"
                "".format(option, section, MAX_INTERPOLATION_DEPTH,
                          rawval))
         InterpolationError.__init__(self, option, section, msg)
         self.args = (option, section, rawval)
 
 class ParsingError(Error):
     """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("Cannot specify both `filename' and `source'. "
                              "Use `source'.")
         elif not filename and not source:
             raise ValueError("Required argument `source' not given.")
         elif filename:
             source = filename
         Error.__init__(self, 'Source contains parsing errors: %r' % source)
         self.source = source
         self.errors = []
         self.args = (source, )
 
     @property
     def filename(self):
         """Deprecated, use `source'."""
         warnings.warn(
             "The 'filename' attribute will be removed in future versions.  "
             "Use 'source' instead.",
             DeprecationWarning, stacklevel=2
         )
         return self.source
 
     @filename.setter
     def filename(self, value):
         """Deprecated, user `source'."""
         warnings.warn(
             "The 'filename' attribute will be removed in future versions.  "
             "Use 'source' instead.",
             DeprecationWarning, stacklevel=2
         )
         self.source = value
 
     def append(self, lineno, line):
         self.errors.append((lineno, line))
         self.message += '\n\t[line %2d]: %s' % (lineno, line)
 
 class MissingSectionHeaderError(ParsingError):
     """Raised when a key-value pair is found before any section header."""
 
     def __init__(self, filename, lineno, line):
         Error.__init__(
             self,
             'File contains no section headers.\nfile: %r, 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:
     """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):
     """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 % usage
     is considered a user error and raises `InterpolationSyntaxError'."""
 
     _KEYCRE = re.compile(r"%\(([^)]+)\)s")
 
     def before_get(self, parser, section, option, value, defaults):
         L = []
         self._interpolate_some(parser, option, L, value, section, defaults, 1)
         return ''.join(L)
 
     def before_set(self, parser, section, option, value):
         tmp_value = value.replace('%%', '') # escaped percent signs
         tmp_value = self._KEYCRE.sub('', tmp_value) # valid syntax
         if '%' in tmp_value:
             raise ValueError("invalid interpolation syntax in %r at "
                              "position %d" % (value, tmp_value.find('%')))
         return value
 
     def _interpolate_some(self, parser, option, accum, rest, section, map,
                           depth):
         rawval = parser.get(section, option, raw=True, fallback=rest)
         if depth > MAX_INTERPOLATION_DEPTH:
             raise InterpolationDepthError(option, section, rawval)
         while rest:
             p = rest.find("%")
             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 == "%":
                 accum.append("%")
                 rest = rest[2:]
             elif c == "(":
                 m = self._KEYCRE.match(rest)
                 if m is None:
                     raise InterpolationSyntaxError(option, section,
                         "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, rawval, var) from None
                 if "%" in v:
                     self._interpolate_some(parser, option, accum, v,
                                            section, map, depth + 1)
                 else:
                     accum.append(v)
             else:
                 raise InterpolationSyntaxError(
                     option, section,
                     "'%%' must be followed by '%%' or '(', "
                     "found: %r" % (rest,))
 
 class ExtendedInterpolation(Interpolation):
     """Advanced variant of interpolation, supports the syntax used by
     `zc.buildout'. Enables interpolation between sections."""
 
     _KEYCRE = re.compile(r"\$\{([^}]+)\}")
 
     def before_get(self, parser, section, option, value, defaults):
         L = []
         self._interpolate_some(parser, option, L, value, section, defaults, 1)
         return ''.join(L)
 
     def before_set(self, parser, section, option, value):
         tmp_value = value.replace('$$', '') # escaped dollar signs
         tmp_value = self._KEYCRE.sub('', tmp_value) # valid syntax
         if '$' in tmp_value:
             raise ValueError("invalid interpolation syntax in %r at "
                              "position %d" % (value, tmp_value.find('$')))
         return value
 
     def _interpolate_some(self, parser, option, accum, rest, section, map,
                           depth):
         rawval = parser.get(section, option, raw=True, fallback=rest)
         if depth > MAX_INTERPOLATION_DEPTH:
             raise InterpolationDepthError(option, section, rawval)
         while rest:
             p = rest.find("$")
             if p < 0:
                 accum.append(rest)
                 return
             if p > 0:
                 accum.append(rest[:p])
                 rest = rest[p:]
             # p is no longer used
             c = rest[1:2]
             if c == "$":
                 accum.append("$")
                 rest = rest[2:]
             elif c == "{":
                 m = self._KEYCRE.match(rest)
                 if m is None:
                     raise InterpolationSyntaxError(option, section,
                         "bad interpolation variable reference %r" % rest)
                 path = m.group(1).split(':')
                 rest = rest[m.end():]
                 sect = section
                 opt = option
                 try:
                     if len(path) == 1:
                         opt = parser.optionxform(path[0])
                         v = map[opt]
                     elif len(path) == 2:
                         sect = path[0]
                         opt = parser.optionxform(path[1])
                         v = parser.get(sect, opt, raw=True)
                     else:
                         raise InterpolationSyntaxError(
                             option, section,
                             "More than one ':' found: %r" % (rest,))
                 except (KeyError, NoSectionError, NoOptionError):
                     raise InterpolationMissingOptionError(
                         option, section, rawval, ":".join(path)) from None
                 if "$" 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,
                     "'$' must be followed by '$' or '{', "
                     "found: %r" % (rest,))
 
 class LegacyInterpolation(Interpolation):
     """Deprecated interpolation used in old versions of ConfigParser.
     Use BasicInterpolation or ExtendedInterpolation instead."""
 
     _KEYCRE = re.compile(r"%\(([^)]*)\)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 "%(" in value:
                 replace = functools.partial(self._interpolation_replace,
                                             parser=parser)
                 value = self._KEYCRE.sub(replace, value)
                 try:
                     value = value % vars
                 except KeyError as e:
                     raise InterpolationMissingOptionError(
                         option, section, rawval, e.args[0]) from None
             else:
                 break
         if value and "%(" 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 "%%(%s)s" % parser.optionxform(s)
 
 class RawConfigParser(MutableMapping):
     """ConfigParser that does not do interpolation."""
 
     # Regular expressions for parsing section headers and options
     _SECT_TMPL = r"""
         \[                                 # [
         (?P<header>[^]]+)                  # very permissive!
         \]                                 # ]
         """
     _OPT_TMPL = r"""
         (?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 = r"""
         (?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="=|:"), re.VERBOSE)
     # Compiled regular expression for matching options with optional values
     # delimited using typical separators
     OPTCRE_NV = re.compile(_OPT_NV_TMPL.format(delim="=|:"), re.VERBOSE)
     # Compiled regular expression for matching leading whitespace in a line
     NONSPACECRE = re.compile(r"\S")
     # Possible boolean values in the configuration.
     BOOLEAN_STATES = {'': True, 'yes': True, 'true': True, 'on': True,
                       '': False, 'no': False, 'false': False, 'off': False}
 
     def __init__(self, defaults=None, dict_type=_default_dict,
                  allow_no_value=False, *, delimiters=('=', ':'),
                  comment_prefixes=('#', ';'), inline_comment_prefixes=None,
                  strict=True, empty_lines_in_values=True,
                  default_section=DEFAULTSECT,
                  interpolation=_UNSET, converters=_UNSET):
 
         self._dict = dict_type
         self._sections = self._dict()
         self._defaults = self._dict()
         self._converters = ConverterMapping(self)
         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 == ('=', ':'):
             self._optcre = self.OPTCRE_NV if allow_no_value else self.OPTCRE
         else:
             d = "|".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()
         if converters is not _UNSET:
             self._converters.update(converters)
 
     def defaults(self):
         return self._defaults
 
     def sections(self):
         """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):
         """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('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):
         """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):
         """Return a list of option names for the given section name."""
         try:
             opts = self._sections[section].copy()
         except KeyError:
             raise NoSectionError(section) from None
         opts.update(self._defaults)
         return list(opts.keys())
 
     def read(self, filenames, encoding=None):
         """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, (str, os.PathLike)):
             filenames = [filenames]
         read_ok = []
         for filename in filenames:
             try:
                 with open(filename, encoding=encoding) as fp:
                     self._read(fp, filename)
             except OSError:
                 continue
             if isinstance(filename, os.PathLike):
                 filename = os.fspath(filename)
             read_ok.append(filename)
         return read_ok
 
     def read_file(self, f, source=None):
         """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 = '<???>'
         self._read(f, source)
 
     def read_string(self, string, source='<string>'):
         """Read configuration from a given string."""
         sfile = io.StringIO(string)
         self.read_file(sfile, source)
 
     def read_dict(self, dictionary, source='<dict>'):
         """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 = str(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(str(key))
                 if value is not None:
                     value = str(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):
         """Deprecated, use read_file instead."""
         warnings.warn(
             "This method will be removed in future versions.  "
             "Use 'parser.read_file()' instead.",
             DeprecationWarning, stacklevel=2
         )
         self.read_file(fp, source=filename)
 
     def get(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
         """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 _get_conv(self, section, option, conv, *, raw=False, vars=None,
                   fallback=_UNSET, **kwargs):
         try:
             return self._get(section, conv, option, raw=raw, vars=vars,
                              **kwargs)
         except (NoSectionError, NoOptionError):
             if fallback is _UNSET:
                 raise
             return fallback
 
     # getint, getfloat and getboolean provided directly for backwards compat
     def getint(self, section, option, *, raw=False, vars=None,
                fallback=_UNSET, **kwargs):
         return self._get_conv(section, option, int, raw=raw, vars=vars,
                               fallback=fallback, **kwargs)
 
     def getfloat(self, section, option, *, raw=False, vars=None,
                  fallback=_UNSET, **kwargs):
         return self._get_conv(section, option, float, raw=raw, vars=vars,
                               fallback=fallback, **kwargs)
 
     def getboolean(self, section, option, *, raw=False, vars=None,
                    fallback=_UNSET, **kwargs):
         return self._get_conv(section, option, self._convert_to_boolean,
                               raw=raw, vars=vars, fallback=fallback, **kwargs)
 
     def items(self, section=_UNSET, raw=False, vars=None):
         """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().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 popitem(self):
         """Remove a section from the parser and return it as
         a (section_name, section_proxy) tuple. If no section is present, raise
         KeyError.
 
         The section DEFAULT is never returned because it cannot be removed.
         """
         for key in self.sections():
             value = self[key]
             del self[key]
             return key, value
         raise KeyError
 
     def optionxform(self, optionstr):
         return optionstr.lower()
 
     def has_option(self, section, option):
         """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):
         """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) from None
         sectdict[self.optionxform(option)] = value
 
     def write(self, fp, space_around_delimiters=True):
         """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 = " {} ".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):
         """Write a single section to the specified `fp'."""
         fp.write("[{}]\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 + str(value).replace('\n', '\n\t')
             else:
                 value = ""
             fp.write("{}{}\n".format(key, value))
         fp.write("\n")
 
     def remove_option(self, section, option):
         """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) from None
         option = self.optionxform(option)
         existed = option in sectdict
         if existed:
             del sectdict[option]
         return existed
 
     def remove_section(self, section):
         """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.
         if key == self.default_section:
             self._defaults.clear()
         elif key in self._sections:
             self._sections[key].clear()
         self.read_dict({key: value})
 
     def __delitem__(self, key):
         if key == self.default_section:
             raise ValueError("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):
         """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 = sys.maxsize
             # strip inline comments
             inline_prefixes = {p: -1 for p in self._inline_comment_prefixes}
             while comment_start == sys.maxsize and inline_prefixes:
                 next_prefixes = {}
                 for prefix, index in inline_prefixes.items():
                     index = line.find(prefix, index+1)
                     if index == -1:
                         continue
                     next_prefixes[prefix] = index
                     if index == 0 or (index > 0 and line[index-1].isspace()):
                         comment_start = min(comment_start, index)
                 inline_prefixes = next_prefixes
             # strip full line comments
             for prefix in self._comment_prefixes:
                 if line.strip().startswith(prefix):
                     comment_start = 0
                     break
             if comment_start == sys.maxsize:
                 comment_start = None
             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('') # 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('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('option', 'vi', '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)
         self._join_multiline_values()
         # if any parsing errors occurred, raise an exception
         if e:
             raise e
 
     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 = '\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):
         """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 = str(value)
                 vardict[self.optionxform(key)] = value
         return _ChainMap(vardict, sectiondict, self._defaults)
 
     def _convert_to_boolean(self, value):
         """Return a boolean value translating from other types if necessary.
         """
         if value.lower() not in self.BOOLEAN_STATES:
             raise ValueError('Not a boolean: %s' % value)
         return self.BOOLEAN_STATES[value.lower()]
 
     def _validate_value_types(self, *, section="", option="", value=""):
         """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, str):
             raise TypeError("section names must be strings")
         if not isinstance(option, str):
             raise TypeError("option keys must be strings")
         if not self._allow_no_value or value:
             if not isinstance(value, str):
                 raise TypeError("option values must be strings")
 
     @property
     def converters(self):
         return self._converters
 
 class ConfigParser(RawConfigParser):
     """ConfigParser implementing interpolation."""
 
     _DEFAULT_INTERPOLATION = BasicInterpolation()
 
     def set(self, section, option, value=None):
         """Set an option.  Extends RawConfigParser.set by validating type and
         interpolation syntax on the value."""
         self._validate_value_types(option=option, value=value)
         super().set(section, option, value)
 
     def add_section(self, section):
         """Create a new section in the configuration.  Extends
         RawConfigParser.add_section by validating if the section name is
         a string."""
         self._validate_value_types(section=section)
         super().add_section(section)
 
 class SafeConfigParser(ConfigParser):
     """ConfigParser alias for backwards compatibility purposes."""
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         warnings.warn(
             "The SafeConfigParser class has been renamed to ConfigParser "
             "in Python 3.2. This alias will be removed in future versions."
             " Use ConfigParser directly instead.",
             DeprecationWarning, stacklevel=2
         )
 
 class SectionProxy(MutableMapping):
     """A proxy for a single section from a parser."""
 
     def __init__(self, parser, name):
         """Creates a view on a section of the specified `name` in `parser`."""
         self._parser = parser
         self._name = name
         for conv in parser.converters:
             key = 'get' + conv
             getter = functools.partial(self.get, _impl=getattr(parser, key))
             setattr(self, key, getter)
 
     def __repr__(self):
         return '<Section: {}>'.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):
         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()
 
     @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
 
     def get(self, option, fallback=None, *, raw=False, vars=None,
             _impl=None, **kwargs):
         """Get an option value.
 
         Unless `fallback` is provided, `None` will be returned if the option
         is not found.
 
         """
         # If `_impl` is provided, it should be a getter method on the parser
         # object that provides the desired type conversion.
         if not _impl:
             _impl = self._parser.get
         return _impl(self._name, option, raw=raw, vars=vars,
                      fallback=fallback, **kwargs)
 
 class ConverterMapping(MutableMapping):
     """Enables reuse of get*() methods between the parser and section proxies.
 
     If a parser class implements a getter directly, the value for the given
     key will be ``None``. The presence of the converter name here enables
     section proxies to find and use the implementation on the parser class.
     """
 
     GETTERCRE = re.compile(r"^get(?P<name>.+)$")
 
     def __init__(self, parser):
         self._parser = parser
         self._data = {}
         for getter in dir(self._parser):
             m = self.GETTERCRE.match(getter)
             if not m or not callable(getattr(self._parser, getter)):
                 continue
             self._data[m.group('name')] = None   # See class docstring.
 
     def __getitem__(self, key):
         return self._data[key]
 
     def __setitem__(self, key, value):
         try:
             k = 'get' + key
         except TypeError:
             raise ValueError('Incompatible key: {} (type: {})'
                              ''.format(key, type(key)))
         if k == 'get':
             raise ValueError('Incompatible key: cannot use "" as a name')
         self._data[key] = value
         func = functools.partial(self._parser._get_conv, conv=value)
         func.converter = value
         setattr(self._parser, k, func)
         for proxy in self._parser.values():
             getter = functools.partial(proxy.get, _impl=func)
             setattr(proxy, k, getter)
 
     def __delitem__(self, key):
         try:
             k = 'get' + (key or None)
         except TypeError:
             raise KeyError(key)
         del self._data[key]
         for inst in itertools.chain((self._parser,), self._parser.values()):
             try:
                 delattr(inst, k)
             except AttributeError:
                 # don't raise since the entry was present in _data, silently
                 # clean up
                 continue
 
     def __iter__(self):
         return iter(self._data)
 
     def __len__(self):
         return len(self._data)