Template Designer Documentation
===============================
.. highlight:: html+jinja
This document describes the syntax and semantics of the template engine and
will be most useful as reference to those creating Jinja templates. As the
template engine is very flexible the configuration from the application might
be slightly different from here in terms of delimiters and behavior of
undefined values.
Synopsis
--------
A template is simply a text file. It can generate any text-based format
(HTML, XML, CSV, LaTeX, etc.). It doesn't have a specific extension,
``.html`` or ``.xml`` are just fine.
A template contains **variables** or **expressions**, which get replaced with
values when the template is evaluated, and tags, which control the logic of
the template. The template syntax is heavily inspired by Django and Python.
Below is a minimal template that illustrates a few basics. We will cover
the details later in that document::
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en">
<head>
<title>My Webpage</title>
</head>
<body>
<ul id="navigation">
{% for item in navigation %}
<li><a href="{{ item.href }}">{{ item.caption }}</a></li>
{% endfor %}
</ul>
<h1>My Webpage</h1>
{{ a_variable }}
</body>
</html>
This covers the default settings. The application developer might have
changed the syntax from ``{% foo %}`` to ``<% foo %>`` or something similar.
There are two kinds of delimiers. ``{% ... %}`` and ``{{ ... }}``. The first
one is used to execute statements such as for-loops or assign values, the
latter prints the result of the expression to the template.
.. _variables:
Variables
---------
The application passes variables to the templates you can mess around in the
template. Variables may have attributes or elements on them you can access
too. How a variable looks like, heavily depends on the application providing
those.
You can use a dot (``.``) to access attributes of a variable, alternative the
so-called "subscript" syntax (``[]``) can be used. The following lines do
the same::
{{ foo.bar }}
{{ foo['bar'] }}
It's important to know that the curly braces are *not* part of the variable
but the print statement. If you access variables inside tags don't put the
braces around.
If a variable or attribute does not exist you will get back an undefined
value. What you can do with that kind of value depends on the application
configuration, the default behavior is that it evaluates to an empty string
if printed and that you can iterate over it, but every other operation fails.
.. _notes-on-subscriptions:
.. admonition:: Implementation
For convenience sake ``foo.bar`` in Jinja2 does the following things on
the Python layer:
- check if there is an attribute called `bar` on `foo`.
- if there is not, check if there is an item ``'bar'`` in `foo`.
- if there is not, return an undefined object.
``foo['bar']`` on the other hand works mostly the same with the a small
difference in the order:
- check if there is an item ``'bar'`` in `foo`.
- if there is not, check if there is an attribute called `bar` on `foo`.
- if there is not, return an undefined object.
This is important if an object has an item or attribute with the same
name. Additionally there is the :func:`attr` filter that just looks up
attributes.
.. _filters:
Filters
-------
Variables can by modified by **filters**. Filters are separated from the
variable by a pipe symbol (``|``) and may have optional arguments in
parentheses. Multiple filters can be chained. The output of one filter is
applied to the next.
``{{ name|striptags|title }}`` for example will remove all HTML Tags from the
`name` and title-cases it. Filters that accept arguments have parentheses
around the arguments, like a function call. This example will join a list
by spaces: ``{{ list|join(', ') }}``.
The :ref:`builtin-filters` below describes all the builtin filters.
.. _tests:
Tests
-----
Beside filters there are also so called "tests" available. Tests can be used
to test a variable against a common expression. To test a variable or
expression you add `is` plus the name of the test after the variable. For
example to find out if a variable is defined you can do ``name is defined``
which will then return true or false depending on if `name` is defined.
Tests can accept arguments too. If the test only takes one argument you can
leave out the parentheses to group them. For example the following two
expressions do the same::
{% if loop.index is divisibleby 3 %}
{% if loop.index is divisibleby(3) %}
The :ref:`builtin-tests` below describes all the builtin tests.
Comments
--------
To comment-out part of a line in a template, use the comment syntax which is
by default set to ``{# ... #}``. This is useful to comment out parts of the
template for debugging or to add information for other template designers or
yourself::
{# note: disabled template because we no longer user this
{% for user in users %}
...
{% endfor %}
#}
Whitespace Control
------------------
In the default configuration whitespace is not further modified by the
template engine, so each whitespace (spaces, tabs, newlines etc.) is returned
unchanged. If the application configures Jinja to `trim_blocks` the first
newline after a a template tag is removed automatically (like in PHP).
But you can also strip whitespace in templates by hand. If you put an minus
sign (``-``) to the start or end of an block (for example a for tag), a
comment or variable expression you can remove the whitespaces after or before
that block::
{% for item in seq -%}
{{ item }}
{%- endfor %}
This will yield all elements without whitespace between them. If `seq` was
a list of numbers from ``1`` to ``9`` the output would be ``123456789``.
If :ref:`line-statements` are enabled they strip leading whitespace
automatically up to the beginning of the line.
.. admonition:: Note
You must not use a whitespace between the tag and the minus sign.
**valid**::
{%- if foo -%}...{% endif %}
**invalid**::
{% - if foo - %}...{% endif %}
Escaping
--------
It is sometimes desirable or even necessary to have Jinja ignore parts it
would otherwise handle as variables or blocks. For example if the default
syntax is used and you want to use ``{{`` as raw string in the template and
not start a variable you have to use a trick.
The easiest way is to output the variable delimiter (``{{``) by using a
variable expression::
{{ '{{' }}
For bigger sections it makes sense to mark a block `raw`. For example to
put Jinja syntax as example into a template you can use this snippet::
{% raw %}
<ul>
{% for item in seq %}
<li>{{ item }}</li>
{% endfor %}
</ul>
{% endraw %}
.. _line-statements:
Line Statements
---------------
If line statements are enabled by the application it's possible to mark a
line as a statement. For example if the line statement prefix is configured
to ``#`` the following two examples are equivalent::
<ul>
# for item in seq
<li>{{ item }}</li>
# endfor
</ul>
<ul>
{% for item in seq %}
<li>{{ item }}</li>
{% endfor %}
</ul>
The line statement prefix can appear anywhere on the line as long as no text
precedes it. For better readability statements that start a block (such as
`for`, `if`, `elif` etc.) may end with a colon::
# for item in seq:
...
# endfor
.. admonition:: Note
Line statements can span multiple lines if there are open parentheses,
braces or brackets::
<ul>
# for href, caption in [('index.html', 'Index'),
('about.html', 'About')]:
<li><a href="{{ href }}">{{ capti
PyPI 官网下载 | Jinja2-2.0.tar.gz
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PyPI 官网下载 | Jinja2-2.0.tar.gz （225个子文件） 
AUTHORS 283B _speedups.c 6KB setup.cfg 97B CHANGES 1KB default.css 13KB traditional.css 11KB sphinxdoc.css 8KB style.css 6KB style.css 6KB pygments.css 3KB print.css 266B print.css 266B stickysidebar.css 248B rightsidebar.css 187B .DS_Store 6KB .DS_Store 6KB ._.DS_Store 82B ._.DS_Store 82B jinja.el 8KB
templates.html 120KB api.html 104KB extensions.html 99KB genindex.html 35KB switching.html 18KB faq.html 13KB sandbox.html 13KB tricks.html 12KB intro.html 10KB index.html 8KB integration.html 8KB changelog.html 5KB layout.html 3KB search.html 2KB index.html 1KB genindex.html 1KB search.html 1KB index.html 1024B layout.html 1005B index.html 974B index.html 936B layout.html 875B layout.html 871B layout.html 862B helpers.html 443B helpers.html 396B helpers.html 389B _textarea.html 87B page.html 73B broken.html 72B _form.html 68B _input_field.html 64B syntaxerror.html 47B broken.html 26B test.html 4B test.html 4B .ignore 0B .ignore 0B .ignore 0B MANIFEST.in 243B interface.js 78KB jquery.js 53KB searchtools.js 13KB doctools.js 10KB jinja.js 504B jinja.js 504B searchindex.json 32KB LICENSE 2KB Makefile 2KB not-zip-safe 1B PKG-INFO 2KB PKG-INFO 2KB info.plist 5KB
metal.png 21KB metal.png 21KB darkmetal.png 21KB darkmetal.png 21KB jinjabanner.png 11KB jinjabanner.png 11KB watermark.png 7KB watermark.png 7KB watermark_blur.png 7KB watermark_blur.png 7KB implementation.png 4KB implementation.png 4KB note.png 2KB note.png 2KB file.png 392B headerbg.png 298B headerbg.png 298B navigation.png 217B navigation.png 217B contents.png 202B plus.png 199B minus.png 199B compiler.py 51KB parser.py 30KB environment.py 29KB nodes.py 24KB utils.py 21KB lexer.py 21KB共 225 条
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