Jinja2 uses a central object called the template :class:`Environment`.
Instances of this class are used to store the configuration, global objects
and are used to load templates from the file system or other locations.
-Even if you are creating templates from string by using the constructor of
-:class:`Template` class, an environment is created automatically for you.
+Even if you are creating templates from strings by using the constructor of
+:class:`Template` class, an environment is created automatically for you,
+albeit a shared one.
Most applications will create one :class:`Environment` object on application
initialization and use that to load templates. In some cases it's however
print template.render(the='variables', go='here')
+Using a template loader rather then passing strings to :class:`Template`
+or :meth:`Environment.from_string` has multiple advantages. Besides being
+a lot easier to use it also enables template inheritance.
+
Unicode
-------
-Jinja2 is using unicode internally which means that you have to pass unicode
+Jinja2 is using Unicode internally which means that you have to pass Unicode
objects to the render function or bytestrings that only consist of ASCII
characters. Additionally newlines are normalized to one end of line
sequence which is per default UNIX style (``\n``).
+Python 2.x supports two ways of representing string objects. One is the
+`str` type and the other is the `unicode` type, both of which extend a type
+called `basestring`. Unfortunately the default is `str` which should not
+be used to store text based information unless only ASCII characters are
+used. With Python 2.6 it is possible to make `unicode` the default on a per
+module level and with Python 3 it will be the default.
+
+To explicitly use a Unicode string you have to prefix the string literal
+with a `u`: ``u'Hänsel und Gretel sagen Hallo'``. That way Python will
+store the string as Unicode by decoding the string with the character
+encoding from the current Python module. If no encoding is specified this
+defaults to 'ASCII' which means that you can't use any non ASCII identifier.
+
+To set a better module encoding add the following comment to the first or
+second line of the Python module using the Unicode literal::
+
+ # -*- coding: utf-8 -*-
+
+We recommend utf-8 as Encoding for Python modules and templates as it's
+possible to represent every Unicode character in utf-8 and because it's
+backwards compatible to ASCII. For Jinja2 the default encoding of templates
+is assumed to be utf-8.
+
+It is not possible to use Jinja2 to process non-Unicode data. The reason
+for this is that Jinja2 uses Unicode already on the language level. For
+example Jinja2 treats the non-breaking space as valid whitespace inside
+expressions which requires knowledge of the encoding or operating on an
+Unicode string.
+
+For more details about Unicode in Python have a look at the excellent
+`Unicode documentation`_.
+
+Another important thing is how Jinja2 is handling string literals in
+templates. A naive implementation would be using Unicode strings for
+all string literals but it turned out in the past that this is problematic
+as some libraries are typechecking against `str` explicitly. For example
+`datetime.strftime` does not accept Unicode arguments. To not break it
+completely Jinja2 is returning `str` for strings that fit into ASCII and
+for everything else `unicode`:
+
+>>> m = Template(u"{% set a, b = 'foo', 'föö' %}").module
+>>> m.a
+'foo'
+>>> m.b
+u'f\xf6\xf6'
+
+
+.. _Unicode documentation: http://docs.python.org/dev/howto/unicode.html
High Level API
--------------
+The high-level API is the API you will use in the application to load and
+render Jinja2 templates. The :ref:`low-level-api` on the other side is only
+useful if you want to dig deeper into Jinja2 or :ref:`develop extensions
+<jinja-extensions>`.
+
.. autoclass:: Environment([options])
- :members: from_string, get_template, join_path, extend
+ :members: from_string, get_template, select_template,
+ get_or_select_template, join_path, extend, compile_expression,
+ compile_templates, list_templates
.. attribute:: shared
.. automethod:: overlay([options])
- .. method:: undefined([hint,] [obj,] name[, exc])
+ .. method:: undefined([hint, obj, name, exc])
Creates a new :class:`Undefined` object for `name`. This is useful
for filters or functions that may return undefined objects for
some operations. All parameters except of `hint` should be provided
as keyword parameters for better readability. The `hint` is used as
error message for the exception if provided, otherwise the error
- message generated from `obj` and `name` automatically. The exception
+ message will be generated from `obj` and `name` automatically. The exception
provided as `exc` is raised if something with the generated undefined
object is done that the undefined object does not allow. The default
exception is :exc:`UndefinedError`. If a `hint` is provided the
possibility to enhance the error message.
.. autoclass:: Template
- :members: make_module, module, new_context
+ :members: module, make_module
.. attribute:: globals
.. autoclass:: jinja2.environment.TemplateStream()
- :members: disable_buffering, enable_buffering
+ :members: disable_buffering, enable_buffering, dump
+
+
+Autoescaping
+------------
+
+.. versionadded:: 2.4
+
+As of Jinja 2.4 the preferred way to do autoescaping is to enable the
+:ref:`autoescape-extension` and to configure a sensible default for
+autoescaping. This makes it possible to enable and disable autoescaping
+on a per-template basis (HTML versus text for instance).
+
+Here a recommended setup that enables autoescaping for templates ending
+in ``'.html'``, ``'.htm'`` and ``'.xml'`` and disabling it by default
+for all other extensions::
+
+ def guess_autoescape(template_name):
+ if template_name is None or '.' not in template_name:
+ return False
+ ext = template_name.rsplit('.', 1)[1]
+ return ext in ('html', 'htm', 'xml')
+
+ env = Environment(autoescape=guess_autoescape,
+ loader=PackageLoader('mypackage'),
+ extensions=['jinja2.ext.autoescape'])
+
+When implementing a guessing autoescape function, make sure you also
+accept `None` as valid template name. This will be passed when generating
+templates from strings.
+
+Inside the templates the behaviour can be temporarily changed by using
+the `autoescape` block (see :ref:`autoescape-overrides`).
.. _identifier-naming:
The closest to regular Python behavior is the `StrictUndefined` which
disallows all operations beside testing if it's an undefined object.
-.. autoclass:: jinja2.runtime.Undefined()
+.. autoclass:: jinja2.Undefined()
+
+ .. attribute:: _undefined_hint
+
+ Either `None` or an unicode string with the error message for
+ the undefined object.
+
+ .. attribute:: _undefined_obj
+
+ Either `None` or the owner object that caused the undefined object
+ to be created (for example because an attribute does not exist).
+
+ .. attribute:: _undefined_name
-.. autoclass:: jinja2.runtime.DebugUndefined()
+ The name for the undefined variable / attribute or just `None`
+ if no such information exists.
-.. autoclass:: jinja2.runtime.StrictUndefined()
+ .. attribute:: _undefined_exception
+
+ The exception that the undefined object wants to raise. This
+ is usually one of :exc:`UndefinedError` or :exc:`SecurityError`.
+
+ .. method:: _fail_with_undefined_error(\*args, \**kwargs)
+
+ When called with any arguments this method raises
+ :attr:`_undefined_exception` with an error message generated
+ from the undefined hints stored on the undefined object.
+
+.. autoclass:: jinja2.DebugUndefined()
+
+.. autoclass:: jinja2.StrictUndefined()
Undefined objects are created by calling :attr:`undefined`.
+.. admonition:: Implementation
+
+ :class:`Undefined` objects are implemented by overriding the special
+ `__underscore__` methods. For example the default :class:`Undefined`
+ class implements `__unicode__` in a way that it returns an empty
+ string, however `__int__` and others still fail with an exception. To
+ allow conversion to int by returning ``0`` you can implement your own::
+
+ class NullUndefined(Undefined):
+ def __int__(self):
+ return 0
+ def __float__(self):
+ return 0.0
+
+ To disallow a method, just override it and raise
+ :attr:`~Undefined._undefined_exception`. Because this is a very common
+ idom in undefined objects there is the helper method
+ :meth:`~Undefined._fail_with_undefined_error` that does the error raising
+ automatically. Here a class that works like the regular :class:`Undefined`
+ but chokes on iteration::
+
+ class NonIterableUndefined(Undefined):
+ __iter__ = Undefined._fail_with_undefined_error
+
The Context
-----------
blocks registered. The last item in each list is the current active
block (latest in the inheritance chain).
+ .. attribute:: eval_ctx
+
+ The current :ref:`eval-context`.
+
+ .. automethod:: jinja2.runtime.Context.call(callable, \*args, \**kwargs)
+
+
+.. admonition:: Implementation
+
+ Context is immutable for the same reason Python's frame locals are
+ immutable inside functions. Both Jinja2 and Python are not using the
+ context / frame locals as data storage for variables but only as primary
+ data source.
+
+ When a template accesses a variable the template does not define, Jinja2
+ looks up the variable in the context, after that the variable is treated
+ as if it was defined in the template.
+
.. _loaders:
All loaders are subclasses of :class:`BaseLoader`. If you want to create your
own loader, subclass :class:`BaseLoader` and override `get_source`.
-.. autoclass:: jinja2.loaders.BaseLoader
+.. autoclass:: jinja2.BaseLoader
:members: get_source, load
Here a list of the builtin loaders Jinja2 provides:
-.. autoclass:: jinja2.loaders.FileSystemLoader
+.. autoclass:: jinja2.FileSystemLoader
+
+.. autoclass:: jinja2.PackageLoader
-.. autoclass:: jinja2.loaders.PackageLoader
+.. autoclass:: jinja2.DictLoader
-.. autoclass:: jinja2.loaders.DictLoader
+.. autoclass:: jinja2.FunctionLoader
-.. autoclass:: jinja2.loaders.FunctionLoader
+.. autoclass:: jinja2.PrefixLoader
-.. autoclass:: jinja2.loaders.PrefixLoader
+.. autoclass:: jinja2.ChoiceLoader
-.. autoclass:: jinja2.loaders.ChoiceLoader
+.. autoclass:: jinja2.ModuleLoader
+
+
+.. _bytecode-cache:
+
+Bytecode Cache
+--------------
+
+Jinja 2.1 and higher support external bytecode caching. Bytecode caches make
+it possible to store the generated bytecode on the file system or a different
+location to avoid parsing the templates on first use.
+
+This is especially useful if you have a web application that is initialized on
+the first request and Jinja compiles many templates at once which slows down
+the application.
+
+To use a bytecode cache, instanciate it and pass it to the :class:`Environment`.
+
+.. autoclass:: jinja2.BytecodeCache
+ :members: load_bytecode, dump_bytecode, clear
+
+.. autoclass:: jinja2.bccache.Bucket
+ :members: write_bytecode, load_bytecode, bytecode_from_string,
+ bytecode_to_string, reset
+
+ .. attribute:: environment
+
+ The :class:`Environment` that created the bucket.
+
+ .. attribute:: key
+
+ The unique cache key for this bucket
+
+ .. attribute:: code
+
+ The bytecode if it's loaded, otherwise `None`.
+
+
+Builtin bytecode caches:
+
+.. autoclass:: jinja2.FileSystemBytecodeCache
+
+.. autoclass:: jinja2.MemcachedBytecodeCache
Utilities
These helper functions and classes are useful if you add custom filters or
functions to a Jinja2 environment.
-.. autofunction:: jinja2.filters.environmentfilter
+.. autofunction:: jinja2.environmentfilter
-.. autofunction:: jinja2.filters.contextfilter
+.. autofunction:: jinja2.contextfilter
-.. autofunction:: jinja2.utils.environmentfunction
+.. autofunction:: jinja2.evalcontextfilter
-.. autofunction:: jinja2.utils.contextfunction
+.. autofunction:: jinja2.environmentfunction
+
+.. autofunction:: jinja2.contextfunction
+
+.. autofunction:: jinja2.evalcontextfunction
.. function:: escape(s)
- Convert the characters &, <, >, and " in string s to HTML-safe sequences.
- Use this if you need to display text that might contain such characters
- in HTML. This function will not escaped objects that do have an HTML
- representation such as already escaped data.
+ Convert the characters ``&``, ``<``, ``>``, ``'``, and ``"`` in string `s`
+ to HTML-safe sequences. Use this if you need to display text that might
+ contain such characters in HTML. This function will not escaped objects
+ that do have an HTML representation such as already escaped data.
+
+ The return value is a :class:`Markup` string.
-.. autofunction:: jinja2.utils.clear_caches
+.. autofunction:: jinja2.clear_caches
-.. autoclass:: jinja2.utils.Markup
+.. autofunction:: jinja2.is_undefined
+
+.. autoclass:: jinja2.Markup([string])
+ :members: escape, unescape, striptags
+
+.. admonition:: Note
+
+ The Jinja2 :class:`Markup` class is compatible with at least Pylons and
+ Genshi. It's expected that more template engines and framework will pick
+ up the `__html__` concept soon.
Exceptions
----------
-.. autoexception:: jinja2.exceptions.TemplateError
+.. autoexception:: jinja2.TemplateError
+
+.. autoexception:: jinja2.UndefinedError
-.. autoexception:: jinja2.exceptions.UndefinedError
+.. autoexception:: jinja2.TemplateNotFound
-.. autoexception:: jinja2.exceptions.TemplateNotFound
+.. autoexception:: jinja2.TemplatesNotFound
-.. autoexception:: jinja2.exceptions.TemplateSyntaxError
+.. autoexception:: jinja2.TemplateSyntaxError
.. attribute:: message
unicode strings is that Python 2.x is not using unicode for exceptions
and tracebacks as well as the compiler. This will change with Python 3.
-.. autoexception:: jinja2.exceptions.TemplateAssertionError
+.. autoexception:: jinja2.TemplateAssertionError
.. _writing-filters:
publication date: {{ article.pub_date|datetimeformat('%d-%m-%Y') }}
Filters can also be passed the current template context or environment. This
-is useful if a filters wants to return an undefined value or check the current
-:attr:`~Environment.autoescape` setting. For this purpose two decorators
-exist: :func:`environmentfilter` and :func:`contextfilter`.
+is useful if a filter wants to return an undefined value or check the current
+:attr:`~Environment.autoescape` setting. For this purpose three decorators
+exist: :func:`environmentfilter`, :func:`contextfilter` and
+:func:`evalcontextfilter`.
Here a small example filter that breaks a text into HTML line breaks and
paragraphs and marks the return value as safe HTML string if autoescaping is
enabled::
import re
- from jinja2 import environmentfilter, Markup, escape
+ from jinja2 import evalcontextfilter, Markup, escape
_paragraph_re = re.compile(r'(?:\r\n|\r|\n){2,}')
- @environmentfilter
- def nl2br(environment, value):
+ @evalcontextfilter
+ def nl2br(eval_ctx, value):
result = u'\n\n'.join(u'<p>%s</p>' % p.replace('\n', '<br>\n')
for p in _paragraph_re.split(escape(value)))
- if environment.autoescape:
+ if eval_ctx.autoescape:
result = Markup(result)
return result
active :class:`Context` rather then the environment.
+.. _eval-context:
+
+Evaluation Context
+------------------
+
+The evaluation context (short eval context or eval ctx) is a new object
+introducted in Jinja 2.4 that makes it possible to activate and deactivate
+compiled features at runtime.
+
+Currently it is only used to enable and disable the automatic escaping but
+can be used for extensions as well.
+
+In previous Jinja versions filters and functions were marked as
+environment callables in order to check for the autoescape status from the
+environment. In new versions it's encouraged to check the setting from the
+evaluation context instead.
+
+Previous versions::
+
+ @environmentfilter
+ def filter(env, value):
+ result = do_something(value)
+ if env.autoescape:
+ result = Markup(result)
+ return result
+
+In new versions you can either use a :func:`contextfilter` and access the
+evaluation context from the actual context, or use a
+:func:`evalcontextfilter` which directly passes the evaluation context to
+the function::
+
+ @contextfilter
+ def filter(context, value):
+ result = do_something(value)
+ if context.eval_ctx.autoescape:
+ result = Markup(result)
+ return result
+
+ @evalcontextfilter
+ def filter(eval_ctx, value):
+ result = do_something(value)
+ if eval_ctx.autoescape:
+ result = Markup(result)
+ return result
+
+The evaluation context must not be modified at runtime. Modifications
+must only happen with a :class:`nodes.EvalContextModifier` and
+:class:`nodes.ScopedEvalContextModifier` from an extension, not on the
+eval context object itself.
+
+.. autoclass:: jinja2.nodes.EvalContext
+
+ .. attribute:: autoescape
+
+ `True` or `False` depending on if autoescaping is active or not.
+
+ .. attribute:: volatile
+
+ `True` if the compiler cannot evaluate some expressions at compile
+ time. At runtime this should always be `False`.
+
+
.. _writing-tests:
Custom Tests
------------
-Tests work like filters just that there is no way for a filter to get access
+Tests work like filters just that there is no way for a test to get access
to the environment or context and that they can't be chained. The return
-value of a filter should be `True` or `False`. The purpose of a filter is to
+value of a test should be `True` or `False`. The purpose of a test is to
give the template designers the possibility to perform type and conformability
checks.
-Here a simple filter that checks if a variable is a prime number::
+Here a simple test that checks if a variable is a prime number::
import math
to all :meth:`~Template.render` calls.
+.. _low-level-api:
+
Low Level API
-------------
The low level API exposes functionality that can be useful to understand some
implementation details, debugging purposes or advanced :ref:`extension
-<jinja-extensions>` techniques.
+<jinja-extensions>` techniques. Unless you know exactly what you are doing we
+don't recommend using any of those.
.. automethod:: Environment.lex
.. automethod:: Environment.parse
+.. automethod:: Environment.preprocess
+
.. automethod:: Template.new_context
.. method:: Template.root_render_func(context)
This attribute is `False` if there is a newer version of the template
available, otherwise `True`.
+
+.. admonition:: Note
+
+ The low-level API is fragile. Future Jinja2 versions will try not to
+ change it in a backwards incompatible way but modifications in the Jinja2
+ core may shine through. For example if Jinja2 introduces a new AST node
+ in later versions that may be returned by :meth:`~Environment.parse`.
+
+The Meta API
+------------
+
+.. versionadded:: 2.2
+
+The meta API returns some information about abstract syntax trees that
+could help applications to implement more advanced template concepts. All
+the functions of the meta API operate on an abstract syntax tree as
+returned by the :meth:`Environment.parse` method.
+
+.. autofunction:: jinja2.meta.find_undeclared_variables
+
+.. autofunction:: jinja2.meta.find_referenced_templates
projects / jinja2.git / blobdiff