**README** for PLIB Version 0.4.3

:Author:        Peter A. Donis
:Release Date:  28 June 2008

The PLIB package contains a number of useful sub-packages and
modules, all within the ``plib`` package namespace in order to
minimize clutter in the top-level namespace of your Python
installation. Each sub-directory of the ``plib`` directory
contains a sub-package, except for the ``test`` directory, which
contains the PLIB test suite. The source distribution also
contains an ``examples`` directory, which has example programs
using PLIB, and a ``scripts`` directory, which has a few
post-install scripts. (The ``SetupHelper`` directory in the
source distribution is not installed; it contains a helper
module for PLIB's setup script. SetupHelper is available as
a separate package from PyPI under the name ``setuphelper``.)

The PLIB Sub-Packages
=====================

The individual sub-packages and modules contain docstrings
with more information about their usage; here they are
briefly listed and described.

PLIB.CLASSES
------------

Each of the modules in this sub-package contains a single
class with the same name; the ``ModuleProxy`` class from
the ``PLIB.UTILS`` sub-package is used to make all the classes
appear in the ``plib.classes`` namespace. See the sub-package
and ``ModuleProxy`` docstrings for more information.

The classes in this sub-package are a miscellaneous group,
included for no other reason than that I have found them
useful.

PLIB.EXTENSIONS
---------------

This sub-package provides a namespace for functions (and
possibly, in the future, other objects) exported from an
extension module written using the Python/C API. The general
philosophy of PLIB is to do everything possible in pure
Python, so the only functions that appear in this sub-package
are those which by their very nature cannot be done in pure
Python.

PLIB.GUI
--------

This is the largest sub-package, and contains a simple GUI
application framework with two main features:

- It lets the same high-level code work with a number of
  different underlying GUI toolkits. Currently supported:
  Qt (versions 3 and 4), KDE, wxWidgets, and GTK. (The original
  reason for writing this sub-package was that wxWidgets doesn't
  use Qt and I like the Qt/KDE widgets better, but I wanted
  code that would run cross-platform.)

- It allows you to express the layout of your GUI in terms
  of Python lists and dicts, enabling a much more declarative
  and easy to read (and maintain) coding style.

Other than selecting the toolkit (which may not be necessary:
the main module of the sub-package can 'auto-detect' which
toolkit to use--the ``plib-setup-gui`` post-install script
does most of the work to enable this--so you only need to
override if you don't like the default), you should not have
to worry about any toolkit internal details; the goal of this
sub-package is to make them all look the same to your code.

Note that the GTK toolkit support in this sub-package is
"experimental" and may be removed if it proves to be more
trouble than it's worth. It's currently included because
wxWidgets' behavior when using GTK as its underlying GUI
framework has some quirks that I haven't been able to work
around yet. However, the GTK implementation of a number of
widgets (particularly tables and list/tree views) is much
less capable than the wxWidgets one, so the Python code for
GTK ends up relying much more on ugly hacks.

PLIB.INI
--------

This sub-package implements an abstract 'INI file' API that
uses ``ConfigParser`` on POSIX systems, and the Windows registry
on Windows systems. As with the ``PLIB.GUI`` sub-package, the
goal is to hide the internal details of the configuration
storage from your code, so all you have to do is define
your configuration structure, again using native Python data
types (lists and dicts).

PLIB.STDLIB
-----------

This is a namespace for various functions and classes that
extend or emulate the Python standard library. Some,
like the ``cached_property`` decorator, are implementations of
patterns that have been known for some time, but which don't
have a "canonical" version in the stdlib yet; rather than
have PLIB depend on some other third-party package, I've
simply provided my own implementations here. Others, like
the ``abstractcontainer`` class and its subclasses, are
re-implementations of standard Python data structures,
written to enable PLIB to make as many things as possible
look like those data structures without having to subclass
the built-ins (which has some downsides for the use cases
I've had thus far--see the docstrings for more information).

This sub-package also contains modules that extend or
provide alternate interfaces to Python standard library
modules. The ``async`` module contains a dispatcher class
with similar functionality to the ``asyncore`` module, and
the ``AsyncServer`` module contains client and server classes
that use this base to provide a similar API to the classes
in the ``SocketServer`` module, but using asynchronous I/O.
The ``options`` module provides an easier-to-use overlay for
the ``optparse`` module which allows you to express your option
configuration in the form of Python lists, tuples, and dicts,
and also adds some minimal argument checking functionality.

PLIB.UTILS
----------

This sub-package contains a few miscellaneous useful
functions, and also the ``ModuleProxy`` class referred to
above. It also contains the ``version`` module, which has
functions for manipulating version number strings and
tuples.

PLIB.XML
--------

This sub-package requires the LXML extension, which uses
the very fast libxml2 library but provides a Pythonic API
similar to ElementTree. The reason for using LXML instead
of ElementTree itself is that LXML has two key additional
features:

- Custom element classes: the ``classes`` module in this
  sub-package builds on this feature by using metaclasses
  to automate DTD generation and validation, but the
  feature is also great for many XML applications.

- Full and *fast* XPATH support: this was key in the XML
  application that first prompted me to write this sub-package.
  Yes, I know there are plenty of other Python XML packages
  that do XPATH; the point is to have it *plus* the standard
  ElementTree API *plus* the speed of libxml2.

Installation
============

To install PLIB, you can simply run::

    $ python setup.py install

at a shell prompt from the directory into which you
unzipped the source tarball (the same directory that this
README file is in). This will install PLIB and then
run each of the post-install scripts in the scripts
directory.

Example Programs
================

PLIB comes with example programs that illustrate key features
of the package. After installation, these can be found in the
``$PREFIX/share/plib/examples`` directory. If you have a
POSIX system (Linux or Mac OSX), the ``plib-setup-examples``
post-install script will install symlinks to the example
programs in the ``$PREFIX/bin`` directory.

The Zen of PLIB
===============

There is no single unifying purpose or theme to PLIB, but
like Python itself, it does have a 'Zen' of sorts:

- Express everything possible in terms of built-in Python
  data structures.

- Once you've expressed it that way, what the code is
  going to do with it should be obvious.

- Avoid boilerplate code, *and* boilerplate data. Every
  piece of data your program needs should have one and
  only one source.

Copyright and License
=====================

PLIB is Copyright (C) 2008 by Peter A. Donis.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version. (See the LICENSE file for a
copy of version 2 of the License.)

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
