path: root/Doc/lib/libcfgparser.tex

\section{\module{ConfigParser} ---
         Configuration file parser}

\declaremodule{standard}{ConfigParser}
\modulesynopsis{Configuration file parser.}
\moduleauthor{Ken Manheimer}{klm@zope.com}
\moduleauthor{Barry Warsaw}{bwarsaw@python.org}
\moduleauthor{Eric S. Raymond}{esr@thyrsus.com}
\sectionauthor{Christopher G. Petrilli}{petrilli@amber.org}

This module defines the class \class{ConfigParser}.
\indexii{.ini}{file}\indexii{configuration}{file}\index{ini file}
\index{Windows ini file}
The \class{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.

\begin{notice}[warning]
  This library does \emph{not} interpret or write the value-type
  prefixes used in the Windows Registry extended version of INI syntax.
\end{notice}

The configuration file consists of sections, led by a
\samp{[section]} header and followed by \samp{name: value} entries,
with continuations in the style of \rfc{822}; \samp{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
\code{DEFAULT} section.  Additional defaults can be provided on
initialization and retrieval.  Lines beginning with \character{\#} or
\character{;} are ignored and may be used to provide comments.

For example:

\begin{verbatim}
[My Section]
foodir: %(dir)s/whatever
dir=frob
\end{verbatim}

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

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

\begin{classdesc}{RawConfigParser}{\optional{defaults}}
The basic configuration object.  When \var{defaults} is given, it is
initialized into the dictionary of intrinsic defaults.  This class
does not support the magical interpolation behavior.
\versionadded{2.3}
\end{classdesc}

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

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

\begin{classdesc}{SafeConfigParser}{\optional{defaults}}
Derived class of \class{ConfigParser} that implements a more-sane
variant of the magical interpolation feature.  This implementation is
more predictable as well.
% XXX Need to explain what's safer/more predictable about it.
New applications should prefer this version if they don't need to be
compatible with older versions of Python.
\versionadded{2.3}
\end{classdesc}

\begin{excdesc}{NoSectionError}
Exception raised when a specified section is not found.
\end{excdesc}

\begin{excdesc}{DuplicateSectionError}
Exception raised if \method{add_section()} is called with the name of
a section that is already present.
\end{excdesc}

\begin{excdesc}{NoOptionError}
Exception raised when a specified option is not found in the specified 
section.
\end{excdesc}

\begin{excdesc}{InterpolationError}
Base class for exceptions raised when problems occur performing string
interpolation.
\end{excdesc}

\begin{excdesc}{InterpolationDepthError}
Exception raised when string interpolation cannot be completed because
the number of iterations exceeds \constant{MAX_INTERPOLATION_DEPTH}.
Subclass of \exception{InterpolationError}.
\end{excdesc}

\begin{excdesc}{InterpolationMissingOptionError}
Exception raised when an option referenced from a value does not exist.
Subclass of \exception{InterpolationError}.
\versionadded{2.3}
\end{excdesc}

\begin{excdesc}{InterpolationSyntaxError}
Exception raised when the source text into which substitutions are
made does not conform to the required syntax.
Subclass of \exception{InterpolationError}.
\versionadded{2.3}
\end{excdesc}

\begin{excdesc}{MissingSectionHeaderError}
Exception raised when attempting to parse a file which has no section
headers.
\end{excdesc}

\begin{excdesc}{ParsingError}
Exception raised when errors occur attempting to parse a file.
\end{excdesc}

\begin{datadesc}{MAX_INTERPOLATION_DEPTH}
The maximum depth for recursive interpolation for \method{get()} when
the \var{raw} parameter is false.  This is relevant only for the
\class{ConfigParser} class.
\end{datadesc}


\begin{seealso}
  \seemodule{shlex}{Support for a creating \UNIX{} shell-like
                    mini-languages which can be used as an alternate
                    format for application configuration files.}
\end{seealso}


\subsection{RawConfigParser Objects \label{RawConfigParser-objects}}

\class{RawConfigParser} instances have the following methods:

\begin{methoddesc}{defaults}{}
Return a dictionary containing the instance-wide defaults.
\end{methoddesc}

\begin{methoddesc}{sections}{}
Return a list of the sections available; \code{DEFAULT} is not
included in the list.
\end{methoddesc}

\begin{methoddesc}{add_section}{section}
Add a section named \var{section} to the instance.  If a section by
the given name already exists, \exception{DuplicateSectionError} is
raised.
\end{methoddesc}

\begin{methoddesc}{has_section}{section}
Indicates whether the named section is present in the
configuration. The \code{DEFAULT} section is not acknowledged.
\end{methoddesc}

\begin{methoddesc}{options}{section}
Returns a list of options available in the specified \var{section}.
\end{methoddesc}

\begin{methoddesc}{has_option}{section, option}
If the given section exists, and contains the given option,
return \constant{True}; otherwise return \constant{False}.
\versionadded{1.6}
\end{methoddesc}

\begin{methoddesc}{read}{filenames}
Read and parse a list of filenames.  If \var{filenames} is a string or
Unicode string, it is treated as a single filename.
If a file named in \var{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 \class{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
\method{readfp()} before calling \method{read()} for any optional
files:

\begin{verbatim}
import ConfigParser, os

config = ConfigParser.ConfigParser()
config.readfp(open('defaults.cfg'))
config.read(['site.cfg', os.path.expanduser('~/.myapp.cfg')])
\end{verbatim}
\end{methoddesc}

\begin{methoddesc}{readfp}{fp\optional{, filename}}
Read and parse configuration data from the file or file-like object in
\var{fp} (only the \method{readline()} method is used).  If
\var{filename} is omitted and \var{fp} has a \member{name} attribute,
that is used for \var{filename}; the default is \samp{<???>}.
\end{methoddesc}

\begin{methoddesc}{get}{section, option}
Get an \var{option} value for the named \var{section}.
\end{methoddesc}

\begin{methoddesc}{getint}{section, option}
A convenience method which coerces the \var{option} in the specified
\var{section} to an integer.
\end{methoddesc}

\begin{methoddesc}{getfloat}{section, option}
A convenience method which coerces the \var{option} in the specified
\var{section} to a floating point number.
\end{methoddesc}

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

\begin{methoddesc}{items}{section}
Return a list of \code{(\var{name}, \var{value})} pairs for each
option in the given \var{section}.
\end{methoddesc}

\begin{methoddesc}{set}{section, option, value}
If the given section exists, set the given option to the specified value;
otherwise raise \exception{NoSectionError}.  \var{value} must be a
string (\class{str} or \class{unicode}); if not, \exception{TypeError}
is raised.
\versionadded{1.6}
\end{methoddesc}

\begin{methoddesc}{write}{fileobject}
Write a representation of the configuration to the specified file
object.  This representation can be parsed by a future \method{read()}
call.
\versionadded{1.6}
\end{methoddesc}

\begin{methoddesc}{remove_option}{section, option}
Remove the specified \var{option} from the specified \var{section}.
If the section does not exist, raise \exception{NoSectionError}. 
If the option existed to be removed, return \constant{True};
otherwise return \constant{False}.
\versionadded{1.6}
\end{methoddesc}

\begin{methoddesc}{remove_section}{section}
Remove the specified \var{section} from the configuration.
If the section in fact existed, return \code{True}.
Otherwise return \code{False}.
\end{methoddesc}

\begin{methoddesc}{optionxform}{option}
Transforms the option name \var{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 \var{option}; subclasses may override this or client code
can set an attribute of this name on instances to affect this
behavior.  Setting this to \function{str()}, for example, would make
option names case sensitive.
\end{methoddesc}


\subsection{ConfigParser Objects \label{ConfigParser-objects}}

The \class{ConfigParser} class extends some methods of the
\class{RawConfigParser} interface, adding some optional arguments.
The \class{SafeConfigParser} class implements the same extended
interface.

\begin{methoddesc}{get}{section, option\optional{, raw\optional{, vars}}}
Get an \var{option} value for the named \var{section}.  All the
\character{\%} interpolations are expanded in the return values, based
on the defaults passed into the constructor, as well as the options
\var{vars} provided, unless the \var{raw} argument is true.
\end{methoddesc}

\begin{methoddesc}{items}{section\optional{, raw\optional{, vars}}}
Return a list of \code{(\var{name}, \var{value})} pairs for each
option in the given \var{section}. Optional arguments have the
same meaning as for the \method{get()} method.
\versionadded{2.3}
\end{methoddesc}