
``configparser`` --- Configuration file parser
**********************************************

This module defines the class ``ConfigParser``.   The ``ConfigParser``
class implements a basic configuration file parser language which
provides a structure similar to what you would find on Microsoft
Windows INI files.  You can use this to write Python programs which
can be customized by end users easily.

Note: This library does *not* interpret or write the value-type prefixes
  used in the Windows Registry extended version of INI syntax.

See also:

   Module ``shlex``
      Support for a creating Unix shell-like mini-languages which can
      be used as an alternate format for application configuration
      files.

   Module ``json``
      The json module implements a subset of JavaScript syntax which
      can also be used for this purpose.

The configuration file consists of sections, led by a ``[section]``
header and followed by ``name: value`` entries, with continuations in
the style of **RFC 822** (see section 3.1.1, "LONG HEADER FIELDS");
``name=value`` is also accepted.  Note that leading whitespace is
removed from values. The optional values can contain format strings
which refer to other values in the same section, or values in a
special ``DEFAULT`` section.  Additional defaults can be provided on
initialization and retrieval.  Lines beginning with ``'#'`` or ``';'``
are ignored and may be used to provide comments.

Configuration files may include comments, prefixed by specific
characters (``#`` and ``;``).  Comments may appear on their own in an
otherwise empty line, or may be entered in lines holding values or
section names.  In the latter case, they need to be preceded by a
whitespace character to be recognized as a comment. (For backwards
compatibility, only ``;`` starts an inline comment, while ``#`` does
not.)

On top of the core functionality, ``SafeConfigParser`` supports
interpolation.  This means values can contain format strings which
refer to other values in the same section, or values in a special
``DEFAULT`` section. Additional defaults can be provided on
initialization.

For example:

   [My Section]
   foodir: %(dir)s/whatever
   dir=frob
   long: this value continues
      in the next line

would resolve the ``%(dir)s`` to the value of ``dir`` (``frob`` in
this case). All reference expansions are done on demand.

Default values can be specified by passing them into the
``ConfigParser`` constructor as a dictionary.  Additional defaults
may be passed into the ``get()`` method which will override all
others.

Sections are normally stored in a built-in dictionary. An alternative
dictionary type can be passed to the ``ConfigParser`` constructor. For
example, if a dictionary type is passed that sorts its keys, the
sections will be sorted on write-back, as will be the keys within each
section.

class class configparser.RawConfigParser(defaults=None, dict_type=collections.OrderedDict)

   The basic configuration object.  When *defaults* is given, it is
   initialized into the dictionary of intrinsic defaults.  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. This class does not support the magical
   interpolation behavior.

   Changed in version 3.1: The default *dict_type* is
   ``collections.OrderedDict``.

class class configparser.ConfigParser(defaults=None, dict_type=collections.OrderedDict)

   Derived class of ``RawConfigParser`` that implements the magical
   interpolation feature and adds optional arguments to the ``get()``
   and ``items()`` methods.  The values in *defaults* must be
   appropriate for the ``%()s`` string interpolation.  Note that
   *__name__* is an intrinsic default; its value is the section name,
   and will override any value provided in *defaults*.

   All option names used in interpolation will be passed through the
   ``optionxform()`` method just like any other option name reference.
   For example, using the default implementation of ``optionxform()``
   (which converts option names to lower case), the values ``foo
   %(bar)s`` and ``foo %(BAR)s`` are equivalent.

   Changed in version 3.1: The default *dict_type* is
   ``collections.OrderedDict``.

class class configparser.SafeConfigParser(defaults=None, dict_type=collections.OrderedDict)

   Derived class of ``ConfigParser`` that implements a more-sane
   variant of the magical interpolation feature.  This implementation
   is more predictable as well. New applications should prefer this
   version if they don't need to be compatible with older versions of
   Python.

   Changed in version 3.1: The default *dict_type* is
   ``collections.OrderedDict``.

exception exception configparser.Error

   Base class for all other configparser exceptions.

exception exception configparser.NoSectionError

   Exception raised when a specified section is not found.

exception exception configparser.DuplicateSectionError

   Exception raised if ``add_section()`` is called with the name of a
   section that is already present.

exception exception configparser.NoOptionError

   Exception raised when a specified option is not found in the
   specified  section.

exception exception configparser.InterpolationError

   Base class for exceptions raised when problems occur performing
   string interpolation.

exception exception configparser.InterpolationDepthError

   Exception raised when string interpolation cannot be completed
   because the number of iterations exceeds
   ``MAX_INTERPOLATION_DEPTH``. Subclass of ``InterpolationError``.

exception exception configparser.InterpolationMissingOptionError

   Exception raised when an option referenced from a value does not
   exist. Subclass of ``InterpolationError``.

exception exception configparser.InterpolationSyntaxError

   Exception raised when the source text into which substitutions are
   made does not conform to the required syntax. Subclass of
   ``InterpolationError``.

exception exception configparser.MissingSectionHeaderError

   Exception raised when attempting to parse a file which has no
   section headers.

exception exception configparser.ParsingError

   Exception raised when errors occur attempting to parse a file.

configparser.MAX_INTERPOLATION_DEPTH

   The maximum depth for recursive interpolation for ``get()`` when
   the *raw* parameter is false.  This is relevant only for the
   ``ConfigParser`` class.

See also:

   Module ``shlex``
      Support for a creating Unix shell-like mini-languages which can
      be used as an alternate format for application configuration
      files.


RawConfigParser Objects
=======================

``RawConfigParser`` instances have the following methods:

RawConfigParser.defaults()

   Return a dictionary containing the instance-wide defaults.

RawConfigParser.sections()

   Return a list of the sections available; ``DEFAULT`` is not
   included in the list.

RawConfigParser.add_section(section)

   Add a section named *section* to the instance.  If a section by the
   given name already exists, ``DuplicateSectionError`` is raised. If
   the name ``DEFAULT`` (or any of it's case-insensitive variants) is
   passed, ``ValueError`` is raised.

RawConfigParser.has_section(section)

   Indicates whether the named section is present in the
   configuration. The ``DEFAULT`` section is not acknowledged.

RawConfigParser.options(section)

   Returns a list of options available in the specified *section*.

RawConfigParser.has_option(section, option)

   If the given section exists, and contains the given option, return
   ``True``; otherwise return ``False``.

RawConfigParser.read(filenames)

   Attempt to read and parse a list of filenames, returning a list of
   filenames which were successfully parsed.  If *filenames* is a
   string, it is treated as a single filename. If a file named in
   *filenames* cannot be opened, that file will be ignored.  This is
   designed so that you can specify a list of potential configuration
   file locations (for example, the current directory, the user's home
   directory, and some system-wide directory), and all existing
   configuration files in the list will be read.  If none of the named
   files exist, the ``ConfigParser`` instance will contain an empty
   dataset. An application which requires initial values to be loaded
   from a file should load the required file or files using
   ``readfp()`` before calling ``read()`` for any optional files:

      import configparser, os

      config = configparser.ConfigParser()
      config.readfp(open('defaults.cfg'))
      config.read(['site.cfg', os.path.expanduser('~/.myapp.cfg')])

RawConfigParser.readfp(fp, filename=None)

   Read and parse configuration data from the file or file-like object
   in *fp* (only the ``readline()`` method is used).  The file-like
   object must operate in text mode, i.e. return strings from
   ``readline()``.

   If *filename* is omitted and *fp* has a ``name`` attribute, that is
   used for *filename*; the default is ``<???>``.

RawConfigParser.get(section, option)

   Get an *option* value for the named *section*.

RawConfigParser.getint(section, option)

   A convenience method which coerces the *option* in the specified
   *section* to an integer.

RawConfigParser.getfloat(section, option)

   A convenience method which coerces the *option* in the specified
   *section* to a floating point number.

RawConfigParser.getboolean(section, option)

   A convenience method which coerces the *option* in the specified
   *section* to a Boolean value.  Note that the accepted values for
   the option are ``"1"``, ``"yes"``, ``"true"``, and ``"on"``, which
   cause this method to return ``True``, and ``"0"``, ``"no"``,
   ``"false"``, and ``"off"``, which cause it to return ``False``.
   These string values are checked in a case-insensitive manner.  Any
   other value will cause it to raise ``ValueError``.

RawConfigParser.items(section)

   Return a list of ``(name, value)`` pairs for each option in the
   given *section*.

RawConfigParser.set(section, option, value)

   If the given section exists, set the given option to the specified
   value; otherwise raise ``NoSectionError``.  While it is possible to
   use ``RawConfigParser`` (or ``ConfigParser`` with *raw* parameters
   set to true) for *internal* storage of non-string values, full
   functionality (including interpolation and output to files) can
   only be achieved using string values.

RawConfigParser.write(fileobject)

   Write a representation of the configuration to the specified *file
   object*, which must be opened in text mode (accepting strings).
   This representation can be parsed by a future ``read()`` call.

RawConfigParser.remove_option(section, option)

   Remove the specified *option* from the specified *section*. If the
   section does not exist, raise ``NoSectionError``.  If the option
   existed to be removed, return ``True``; otherwise return ``False``.

RawConfigParser.remove_section(section)

   Remove the specified *section* from the configuration. If the
   section in fact existed, return ``True``. Otherwise return
   ``False``.

RawConfigParser.optionxform(option)

   Transforms the option name *option* as found in an input file or as
   passed in by client code to the form that should be used in the
   internal structures. The default implementation returns a lower-
   case version of *option*; subclasses may override this or client
   code can set an attribute of this name on instances to affect this
   behavior.

   You don't necessarily need to subclass a ConfigParser to use this
   method, you can also re-set it on an instance, to a function that
   takes a string argument.  Setting it to ``str``, for example, would
   make option names case sensitive:

      cfgparser = ConfigParser()
      ...
      cfgparser.optionxform = str

   Note that when reading configuration files, whitespace around the
   option names are stripped before ``optionxform()`` is called.


ConfigParser Objects
====================

The ``ConfigParser`` class extends some methods of the
``RawConfigParser`` interface, adding some optional arguments.

ConfigParser.get(section, option, raw=False, vars=None)

   Get an *option* value for the named *section*.  If *vars* is
   provided, it must be a dictionary.  The *option* is looked up in
   *vars* (if provided), *section*, and in *defaults* in that order.

   All the ``'%'`` interpolations are expanded in the return values,
   unless the *raw* argument is true.  Values for interpolation keys
   are looked up in the same manner as the option.

ConfigParser.items(section, raw=False, vars=None)

   Return a list of ``(name, value)`` pairs for each option in the
   given *section*. Optional arguments have the same meaning as for
   the ``get()`` method.


SafeConfigParser Objects
========================

The ``SafeConfigParser`` class implements the same extended interface
as ``ConfigParser``, with the following addition:

SafeConfigParser.set(section, option, value)

   If the given section exists, set the given option to the specified
   value; otherwise raise ``NoSectionError``.  *value* must be a
   string; if it is not, ``TypeError`` is raised.


Examples
========

An example of writing to a configuration file:

   import configparser

   config = configparser.RawConfigParser()

   # When adding sections or items, add them in the reverse order of
   # how you want them to be displayed in the actual file.
   # In addition, please note that using RawConfigParser's and the raw
   # mode of ConfigParser's respective set functions, you can assign
   # non-string values to keys internally, but will receive an error
   # when attempting to write to a file or when you get it in non-raw
   # mode. SafeConfigParser does not allow such assignments to take place.
   config.add_section('Section1')
   config.set('Section1', 'int', '15')
   config.set('Section1', 'bool', 'true')
   config.set('Section1', 'float', '3.1415')
   config.set('Section1', 'baz', 'fun')
   config.set('Section1', 'bar', 'Python')
   config.set('Section1', 'foo', '%(bar)s is %(baz)s!')

   # Writing our configuration file to 'example.cfg'
   with open('example.cfg', 'w') as configfile:
       config.write(configfile)

An example of reading the configuration file again:

   import configparser

   config = configparser.RawConfigParser()
   config.read('example.cfg')

   # getfloat() raises an exception if the value is not a float
   # getint() and getboolean() also do this for their respective types
   float = config.getfloat('Section1', 'float')
   int = config.getint('Section1', 'int')
   print(float + int)

   # Notice that the next output does not interpolate '%(bar)s' or '%(baz)s'.
   # This is because we are using a RawConfigParser().
   if config.getboolean('Section1', 'bool'):
       print(config.get('Section1', 'foo'))

To get interpolation, you will need to use a ``ConfigParser`` or
``SafeConfigParser``:

   import configparser

   config = configparser.ConfigParser()
   config.read('example.cfg')

   # Set the third, optional argument of get to 1 if you wish to use raw mode.
   print(config.get('Section1', 'foo', 0)) # -> "Python is fun!"
   print(config.get('Section1', 'foo', 1)) # -> "%(bar)s is %(baz)s!"

   # The optional fourth argument is a dict with members that will take
   # precedence in interpolation.
   print(config.get('Section1', 'foo', 0, {'bar': 'Documentation',
                                           'baz': 'evil'}))

Defaults are available in all three types of ConfigParsers. They are
used in interpolation if an option used is not defined elsewhere.

   import configparser

   # New instance with 'bar' and 'baz' defaulting to 'Life' and 'hard' each
   config = configparser.SafeConfigParser({'bar': 'Life', 'baz': 'hard'})
   config.read('example.cfg')

   print(config.get('Section1', 'foo')) # -> "Python is fun!"
   config.remove_option('Section1', 'bar')
   config.remove_option('Section1', 'baz')
   print(config.get('Section1', 'foo')) # -> "Life is hard!"

The function ``opt_move`` below can be used to move options between
sections:

   def opt_move(config, section1, section2, option):
       try:
           config.set(section2, option, config.get(section1, option, 1))
       except configparser.NoSectionError:
           # Create non-existent section
           config.add_section(section2)
           opt_move(config, section1, section2, option)
       else:
           config.remove_option(section1, option)
