docs/intro.rst

Introduction
============

This is the documentation for the Jinja2 general purpose templating language.
Jinja2 is a library for Python that is designed to be flexible, fast and secure.

If you have any exposure to other text-based template languages, such as Smarty or
Django, you should feel right at home with Jinja2.  It's both designer and
developer friendly by sticking to Python's principles and adding functionality
useful for templating environments.

Prerequisites
-------------

Jinja2 works with Python 2.6.x, 2.7.x and >= 3.3.  If you are using Python
3.2 you can use an older release of Jinja2 (2.6) as support for Python 3.2
was dropped in Jinja2 version 2.7.

If you wish to use the :class:`~jinja2.PackageLoader` class, you will also
need `setuptools`_ or `distribute`_ installed at runtime.

Installation
------------

You have multiple ways to install Jinja2.  If you are unsure what to do, go
with the Python egg or tarball.

As a Python egg (via `easy_install`)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can install the most recent Jinja2 version using `easy_install`_ or `pip`_::

    easy_install Jinja2
    pip install Jinja2

This will install a Jinja2 egg in your Python installation's site-packages
directory.

(If you are installing from the Windows command line omit the `sudo` and make
sure to run the command as user with administrator rights)

From the tarball release
~~~~~~~~~~~~~~~~~~~~~~~~~

1.  Download the most recent tarball from the `download page`_
2.  Unpack the tarball
3.  ``sudo python setup.py install``

Note that you either have to have `setuptools` or `distribute` installed;
the latter is preferred.

This will install Jinja2 into your Python installation's site-packages directory.

Installing the development version
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1.  Install `git`_
2.  ``git clone git://github.com/pallets/jinja.git``
3.  ``cd jinja2``
4.  ``ln -s jinja2 /usr/lib/python2.X/site-packages``

As an alternative to steps 4 you can also do ``python setup.py develop``
which will install the package via `distribute` in development mode.  This also
has the advantage that the C extensions are compiled.

.. _download page: http://pypi.python.org/pypi/Jinja2
.. _distribute: http://pypi.python.org/pypi/distribute 
.. _setuptools: http://peak.telecommunity.com/DevCenter/setuptools
.. _easy_install: http://peak.telecommunity.com/DevCenter/EasyInstall
.. _pip: http://pypi.python.org/pypi/pip
.. _git: http://git-scm.org/


MarkupSafe Dependency
~~~~~~~~~~~~~~~~~~~~~

As of version 2.7 Jinja2 depends on the `MarkupSafe`_ module.  If you
install Jinja2 via `pip` or `easy_install` it will be installed
automatically for you.

.. _MarkupSafe: http://pypi.python.org/pypi/MarkupSafe

Basic API Usage
---------------

This section gives you a brief introduction to the Python API for Jinja2
templates.

The most basic way to create a template and render it is through
:class:`~jinja2.Template`.  This however is not the recommended way to
work with it if your templates are not loaded from strings but the file
system or another data source:

>>> from jinja2 import Template
>>> template = Template('Hello {{ name }}!')
>>> template.render(name='John Doe')
u'Hello John Doe!'

By creating an instance of :class:`~jinja2.Template` you get back a new template
object that provides a method called :meth:`~jinja2.Template.render` which when
called with a dict or keyword arguments expands the template.  The dict
or keywords arguments passed to the template are the so-called "context"
of the template.

What you can see here is that Jinja2 is using unicode internally and the
return value is an unicode string.  So make sure that your application is
indeed using unicode internally.


Experimental Python 3 Support
-----------------------------

Jinja 2.7 brings experimental support for Python >=3.3.  It means that all
unittests pass on the new version, but there might still be small bugs in
there and behavior might be inconsistent.  If you notice any bugs, please
provide feedback in the `Jinja bug tracker`_.

Also please keep in mind that the documentation is written with Python 2
in mind, so you will have to adapt the shown code examples to Python 3 syntax
for yourself.


.. _Jinja bug tracker: http://github.com/pallets/jinja/issues