========
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 1.1.2`_ of the spec.

Logo: `David Phillips`_


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

Pystache is tested with--

* Python 2.4 (requires simplejson `version 2.0.9`_ or earlier)
* Python 2.5 (requires simplejson_)
* Python 2.6
* Python 2.7
* Python 3.1
* 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.

For Python 2.4 we require an earlier version of simplejson since simplejson
stopped officially supporting Python 2.4 in simplejson version 2.1.0.
Earlier versions of simplejson can be installed manually, as follows: ::

    pip install 'simplejson<2.1.0'


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

::

    pip install pystache
    pystache-test

To install and test from source (e.g. from GitHub), see the Develop section.


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 (in the same directory by default
as your class definition)::

    Hello, {{to}}!

Pull it together::

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

For greater control over rendering (e.g. to specify a custom template directory),
use the ``Renderer`` class directly.  One can pass attributes to the class's
constructor or set them on an instance.
To customize template loading on a per-view basis, subclass ``TemplateSpec``.
See the docstrings of the Renderer_ class and TemplateSpec_ class for
more information.


Python 3
========

Pystache has supported Python 3 since version 0.5.1.  Pystache behaves
slightly differently between 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
=======

This section describes how Pystache handles unicode, strings, and encodings.

Internally, Pystache uses `only unicode strings`_ (``str`` in Python 3 and
``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.


Develop
=======

To test from a source distribution (without installing)-- ::

    python test_pystache.py

To test Pystache with multiple versions of Python (with a single command!),
you can use tox_: ::

    pip install tox
    tox

If you do not have all Python versions listed in ``tox.ini``-- ::

    tox -e py26,py32  # for example

The source distribution tests also include doctests and tests from the
Mustache spec.  To include tests from the Mustache spec in your test runs: ::

    git submodule init
    git submodule update

The test harness parses the spec's (more human-readable) yaml files if PyYAML_
is present.  Otherwise, it parses the json files.  To install PyYAML-- ::

    pip install pyyaml

To run a subset of the tests, you can use nose_: ::

    pip install nose
    nosetests --tests pystache/tests/test_context.py:GetValueTests.test_dictionary__key_present

**Running Pystache from source with Python 3.**  Pystache is written in
Python 2 and must be converted with 2to3_ prior to running under Python 3.
The installation process (and tox) do this conversion automatically.

To ``import pystache`` from a source distribution while using Python 3,
be sure that you are importing from a directory containing a converted
version (e.g. from your site-packages directory after manually installing)
and not from the original source directory.  Otherwise, you will get a
syntax error.  You can help ensure this by not running the Python IDE
from the project directory when importing Pystache.


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

There is a `mailing list`_.  Note that there is a bit of a delay between
posting a message and seeing it appear in the mailing list archive.


Authors
=======

::

    >>> context = { 'author': 'Chris Wanstrath', 'maintainer': 'Chris Jerdonek' }
    >>> print pystache.render("Author: {{author}}\nMaintainer: {{maintainer}}", context)
    Author: Chris Wanstrath
    Maintainer: Chris Jerdonek


.. _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
.. _mailing list: http://librelist.com/browser/pystache/
.. _Mustache: http://mustache.github.com/
.. _Mustache spec: https://github.com/mustache/spec
.. _mustache(5): http://mustache.github.com/mustache.5.html
.. _nose: http://somethingaboutorange.com/mrl/projects/nose/0.11.1/testing.html
.. _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
.. _PyYAML: http://pypi.python.org/pypi/PyYAML
.. _Renderer: https://github.com/defunkt/pystache/blob/master/pystache/renderer.py
.. _semantically versioned: http://semver.org
.. _simplejson: http://pypi.python.org/pypi/simplejson/
.. _TemplateSpec: https://github.com/defunkt/pystache/blob/master/pystache/template_spec.py
.. _test: http://packages.python.org/distribute/setuptools.html#test
.. _tox: http://pypi.python.org/pypi/tox
.. _version 1.1.2: https://github.com/mustache/spec/tree/v1.1.2
.. _version 2.0.9: http://pypi.python.org/pypi/simplejson/2.0.9