========
Pystache
========

.. image:: https://s3.amazonaws.com/webdev_bucket/pystache.png

Pystache_ is a Python implementation of Mustache_.
Mustache is a framework-agnostic, logic-free templating system inspired
by ctemplate_ and et_.  Like ctemplate, Mustache "emphasizes
separating logic from presentation: it is impossible to embed application
logic in this template language."

The `mustache(5)`_ man page provides a good introduction to Mustache's
syntax.  For a more complete (and more current) description of Mustache's
behavior, see the official `Mustache spec`_.

Pystache is `semantically versioned`_ and can be found on PyPI_.  This
version of Pystache passes all tests in `version 1.0.3`_ of the spec.

Logo: `David Phillips`_


Requirements
============

Pystache is tested with the following versions of Python:

* Python 2.4 (requires simplejson version 2.0.9 or earlier)
* Python 2.5 (requires simplejson)
* Python 2.6
* Python 2.7
* Python 3.2

JSON support is needed only for the command-line interface and to run the
spec tests.  We require simplejson_ for earlier versions of Python since
Python's json_ module was added in Python 2.6.  Moreover, we require an
earlier version of simplejson for Python 2.4 since simplejson stopped
officially supporting Python 2.4 with version 2.1.0.

An earlier version of simplejson can be installed manually, as follows: ::

    pip install 'simplejson<2.1.0'


Install It
==========

::

    pip install pystache


Use It
======

::

    >>> import pystache
    >>> print pystache.render('Hi {{person}}!', {'person': 'Mom'})
    Hi Mom!

You can also create dedicated view classes to hold your view logic.

Here's your view class (in examples/readme.py)::

    class SayHello(object):

        def to(self):
            return "Pizza"

Like so::

    >>> from pystache.tests.examples.readme import SayHello
    >>> hello = SayHello()

Then your template, say_hello.mustache::

    Hello, {{to}}!

Pull it together::

    >>> renderer = pystache.Renderer()
    >>> print renderer.render(hello)
    Hello, Pizza!


Python 3
========

As of version 0.5.1, Pystache fully supports Python 3.  There are slight
differences in behavior between Pystache running under Python 2 and 3,
as follows:

* In Python 2, the default html-escape function ``cgi.escape()`` does not
  escape single quotes; whereas in Python 3, the default escape function
  ``html.escape()`` does escape single quotes.
* In both Python 2 and 3, the string and file encodings default to
  ``sys.getdefaultencoding()``.  However, this function can return different
  values under Python 2 and 3, even when run from the same system.  Check
  your own system for the behavior on your system, or do not rely on the
  defaults by passing in the encodings explicitly (e.g. to the ``Renderer`` class).


Unicode Handling
================

This section describes Pystache's handling of unicode (e.g. strings and
encodings).

Internally, Pystache uses `only unicode strings`_ (type ``str`` in Python 3 and
type ``unicode`` in Python 2).  For input, Pystache accepts both unicode strings
and byte strings (``bytes`` in Python 3 and ``str`` in Python 2).  For output,
Pystache's template rendering methods return only unicode.

Pystache's ``Renderer`` class supports a number of attributes to control how
Pystache converts byte strings to unicode on input.  These include the
``file_encoding``, ``string_encoding``, and ``decode_errors`` attributes.

The ``file_encoding`` attribute is the encoding the renderer uses to convert
to unicode any files read from the file system.  Similarly, ``string_encoding``
is the encoding the renderer uses to convert any other byte strings encountered
during the rendering process into unicode (e.g. context values that are
encoded byte strings).

The ``decode_errors`` attribute is what the renderer passes as the ``errors``
argument to Python's built-in unicode-decoding function (``str()`` in Python 3
and ``unicode()`` in Python 2).  The valid values for this argument are
``strict``, ``ignore``, and ``replace``.

Each of these attributes can be set via the ``Renderer`` class's constructor
using a keyword argument of the same name.  See the Renderer class's
docstrings for further details.  In addition, the ``file_encoding``
attribute can be controlled on a per-view basis by subclassing the
``TemplateSpec`` class.  When not specified explicitly, these attributes
default to values set in Pystache's ``defaults`` module.


Test It
=======

Use tox_ to test Pystache with multiple versions of Python all at once! ::

    pip install tox
    tox

If you do not have all Python versions listed in ``tox.in``, then

    tox -e py26,py27  # for example

To include tests from the Mustache spec in your test runs: ::

    git submodule init
    git submodule update

You can also test Pystache without tox (but with only a single version of
Python at a time), as below.  To do this, install Distribute_ ::

    pip install distribute


Python 2.7 and Later
--------------------

Then run Distribute's test_: ::

    python setup.py test

This runs 2to3_ when using Python 3.


Python 2.6 and Earlier
----------------------

For Python 2.6 and earlier, use nose_ instead of ``test``: ::

    pip install nose
    python setup.py nosetests


Mailing List
============

As of November 2011, there's a mailing list, pystache@librelist.com.

Archive: http://librelist.com/browser/pystache/

Note: There's a bit of a delay in seeing the latest emails appear
in the archive.


Author
======

::

    >>> context = { 'author': 'Chris Wanstrath', 'email': 'chris@ozmm.org' }
    >>> print pystache.render("{{author}} :: {{email}}", context)
    Chris Wanstrath :: chris@ozmm.org


.. _2to3: http://docs.python.org/library/2to3.html
.. _built-in unicode function: http://docs.python.org/library/functions.html#unicode
.. _ctemplate: http://code.google.com/p/google-ctemplate/
.. _David Phillips: http://davidphillips.us/
.. _Distribute: http://pypi.python.org/pypi/distribute
.. _et: http://www.ivan.fomichev.name/2008/05/erlang-template-engine-prototype.html
.. _json: http://docs.python.org/library/json.html
.. _Mustache: http://mustache.github.com/
.. _Mustache spec: https://github.com/mustache/spec
.. _mustache(5): http://mustache.github.com/mustache.5.html
.. _nose: http://readthedocs.org/docs/nose/en/latest/
.. _only unicode strings: http://docs.python.org/howto/unicode.html#tips-for-writing-unicode-aware-programs
.. _PyPI: http://pypi.python.org/pypi/pystache
.. _Pystache: https://github.com/defunkt/pystache
.. _semantically versioned: http://semver.org
.. _simplejson: http://pypi.python.org/pypi/simplejson/
.. _test: http://packages.python.org/distribute/setuptools.html#test
.. _tox: http://pypi.python.org/pypi/tox
.. _version 1.0.3: https://github.com/mustache/spec/tree/48c933b0bb780875acbfd15816297e263c53d6f7