
\section{\module{pkgutil} ---
         Package extension utility}

\declaremodule{standard}{pkgutil}
\modulesynopsis{Utilities to support extension of packages.}

\versionadded{2.3}

This module provides a single function:

\begin{funcdesc}{extend_path}{path, name}
  Extend the search path for the modules which comprise a package.
  Intended use is to place the following code in a package's
  \file{__init__.py}:

\begin{verbatim}
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)
\end{verbatim}

  This will add to the package's \code{__path__} all subdirectories of
  directories on \code{sys.path} named after the package.  This is
  useful if one wants to distribute different parts of a single
  logical package as multiple directories.

  It also looks for \file{*.pkg} files beginning where \code{*}
  matches the \var{name} argument.  This feature is similar to
  \file{*.pth} files (see the \refmodule{site} module for more
  information), except that it doesn't special-case lines starting
  with \code{import}.  A \file{*.pkg} file is trusted at face value:
  apart from checking for duplicates, all entries found in a
  \file{*.pkg} file are added to the path, regardless of whether they
  exist on the filesystem.  (This is a feature.)

  If the input path is not a list (as is the case for frozen
  packages) it is returned unchanged.  The input path is not
  modified; an extended copy is returned.  Items are only appended
  to the copy at the end.

  It is assumed that \code{sys.path} is a sequence.  Items of
  \code{sys.path} that are not (Unicode or 8-bit) strings referring to
  existing directories are ignored.  Unicode items on \code{sys.path}
  that cause errors when used as filenames may cause this function to
  raise an exception (in line with \function{os.path.isdir()} behavior).
\end{funcdesc}
