================= pyramid_chameleon ================= Overview ======== :mod:`pyramid_chameleon` is a set of bindings that make templates written for the :term:`Chameleon` templating system work under the Pyramid web framework. Installation ============ Install using setuptools, e.g. (within a virtualenv):: $ $myvenv/bin/easy_install pyramid_chameleon Setup ===== There are several ways to make sure that :mod:`pyramid_chameleon` is active. They are completely equivalent: #) Add pyramid_chameleon to the `pyramid.includes` section of your applications main configuration section:: [app:main] ... pyramid.includes = pyramid_chameleon #) Use the ``includeme`` function via ``config.include``:: config.include('pyramid_chameleon') Once activated, files with the ``.pt`` extension are considered to be :term:`Chameleon` templates. .. _using_chameleon_templates: Using Chameleon templates ========================= Once :mod:`pyramid_chameleon` been activated ``.pt`` templates can be loaded either by looking up names that would be found on the :term:`Chameleon` search path or by looking up an absolute asset specification (see :ref:`asset_specifications` for more information). Quick example 1. Look up a template named ``foo.pt`` within the ``templates`` directory of a Python package named ``mypackage``: .. code-block:: python :linenos: @view_config(renderer="mypackage:templates/foo.pt) def sample_view(request): return {'foo':1, 'bar':2} Quick example 2. Look up a template named ``foo.pt`` within the ``templates`` directory of the "current" Python package (the package in which this Python code is defined): .. code-block:: python :linenos: @view_config(renderer="templates/foo.pt) def sample_view(request): return {'foo':1, 'bar':2} Quick example 3: manufacturing a response object using the result of :func:`~pyramid.renderers.render` (a string) using a Chameleon template: .. code-block:: python :linenos: from pyramid.renderers import render from pyramid.response import Response def sample_view(request): result = render('mypackage:templates/foo.pt', {'foo':1, 'bar':2}, request=request) response = Response(result) response.content_type = 'text/plain' return response Here's an example view configuration which uses a Chameleon ZPT renderer registered imperatively: .. code-block:: python :linenos: # config is an instance of pyramid.config.Configurator config.add_view('myproject.views.sample_view', renderer='myproject:templates/foo.pt') Here's an example view configuration which uses a Chameleon text renderer registered imperatively: .. code-block:: python :linenos: config.add_view('myproject.views.sample_view', renderer='myproject:templates/foo.txt') .. _chameleon_zpt_templates: Chameleon ZPT templates ----------------------- :term:`Chameleon` is an implementation of :term:`ZPT` (Zope Page Templates) templating language. The Chameleon engine complies largely with the `Zope Page Template `_ template specification. However, it is significantly faster than the default implementation that is represented by ``zope.pagetemplates``. The language definition documentation for Chameleon ZPT-style templates is available from the `Chameleon website `_. Given a :term:`Chameleon` ZPT template named ``foo.pt`` in a directory in your application named ``templates``, you can render the template as a :term:`renderer` like so: .. code-block:: python :linenos: from pyramid.view import view_config @view_config(renderer='templates/foo.pt') def my_view(request): return {'foo':1, 'bar':2} Two built-in renderers exist for :term:`Chameleon` templates. If the ``renderer`` parameter of a view configuration is an absolute path, a relative path or :term:`asset specification` which has a final path element with a filename extension of ``.pt``, the Chameleon ZPT renderer is used. If the extension is ``.txt``, the :term:`Chameleon` text renderer is used. The behavior of these renderers is the same, except for the engine used to render the template. When a Chameleon renderer is used in a view configuration, the view must return a :term:`Response` object or a Python *dictionary*. If the view callable with an associated template returns a Python dictionary, the named template will be passed the dictionary as its keyword arguments, and the template renderer implementation will return the resulting rendered template in a response to the user. If the view callable returns anything but a Response object or a dictionary, an error will be raised. Before passing keywords to the template, the keyword arguments derived from the dictionary returned by the view are augmented. The callable object -- whatever object was used to define the view -- will be automatically inserted into the set of keyword arguments passed to the template as the ``view`` keyword. If the view callable was a class, the ``view`` keyword will be an instance of that class. Also inserted into the keywords passed to the template are ``renderer_name`` (the string used in the ``renderer`` attribute of the directive), ``renderer_info`` (an object containing renderer-related information), ``context`` (the context resource of the view used to render the template), and ``request`` (the request passed to the view used to render the template). ``request`` is also available as ``req`` in Pyramid 1.3+. .. index:: single: ZPT template (sample) A sample ZPT template ~~~~~~~~~~~~~~~~~~~~~ Here's what a simple :term:`Chameleon` ZPT template used under :app:`Pyramid` might look like: .. code-block:: xml :linenos: ${project} Application

Welcome to ${project}, an application generated by the pyramid web application framework.

Note the use of :term:`Mako` and/or :term:`Genshi` -style ``${replacements}`` above. This is one of the ways that :term:`Chameleon` ZPT differs from standard ZPT. The above template expects to find a ``project`` key in the set of keywords passed in to it via :func:`~pyramid.renderers.render` or :func:`~pyramid.renderers.render_to_response`. Typical ZPT attribute-based syntax (e.g. ``tal:content`` and ``tal:replace``) also works in these templates. .. index:: single: ZPT macros single: Chameleon ZPT macros Using ZPT macros in Pyramid ~~~~~~~~~~~~~~~~~~~~~~~~~~~ When a :term:`renderer` is used to render a template, :app:`Pyramid` makes at least two top-level names available to the template by default: ``context`` and ``request``. One of the common needs in ZPT-based templates is to use one template's "macros" from within a different template. In Zope, this is typically handled by retrieving the template from the ``context``. But the context in :app:`Pyramid` is a :term:`resource` object, and templates cannot usually be retrieved from resources. To use macros in :app:`Pyramid`, you need to make the macro template itself available to the rendered template by passing the macro template, or even the macro itself, *into* the rendered template. To do this you can use the :func:`pyramid.renderers.get_renderer` API to retrieve the macro template, and pass it into the template being rendered via the dictionary returned by the view. For example, using a :term:`view configuration` via a :class:`~pyramid.view.view_config` decorator that uses a :term:`renderer`: .. code-block:: python :linenos: from pyramid.renderers import get_renderer from pyramid.view import view_config @view_config(renderer='templates/mytemplate.pt') def my_view(request): main = get_renderer('templates/master.pt').implementation() return {'main':main} Where ``templates/master.pt`` might look like so: .. code-block:: xml :linenos:

Hello Fred!

And ``templates/mytemplate.pt`` might look like so: .. code-block:: xml :linenos: Chris .. index:: single: Using a master page .. _using_master_page: Using a master page ~~~~~~~~~~~~~~~~~~~ You can also use macros and slots to create a master page that can be used by all your templates. This is very similar to using a macro from another template but uses the `IBeforeRender` event subscriber to make the macros available to any template. .. code-block:: python :linenos: from pyramid.renderers import get_renderer from pyramid.interfaces import IBeforeRender from pyramid.events import subscriber @subscriber(IBeforeRender) def globals_factory(event): master = get_renderer('templates/master.pt').implementation() event['master'] = master Where ``templates/master.pt`` provides a whole page with slots to be filled by views: .. code-block:: xml :linenos: Title goes here
© Pylons Project
And ``templates/index.pt`` fills the relevant slots: .. code-block:: xml :linenos: Welcome to Pyramid Chameleon

Pyramid Chameleon

Chameleon is an XML-based templating language

 .. index:: single: Chameleon text templates .. _chameleon_text_templates: Chameleon text templates ------------------------ :mod:`pyramid_chameleon` also allows for the use of templates which are composed entirely of non-XML text via :term:`Chameleon`. To do so, you can create templates that are entirely composed of text except for ``${name}`` -style substitution points. Here's an example usage of a Chameleon text template. Create a file on disk named ``mytemplate.txt`` in your project's ``templates`` directory with the following contents: .. code-block:: text Hello, ${name}! Then in your project's ``views.py`` module, you can create a view which renders this template: .. code-block:: python :linenos: from pyramid.view import view_config @view_config(renderer='templates/mytemplate.txt') def my_view(request): return {'name':'world'} When the template is rendered, it will show: .. code-block:: text Hello, world! If you'd rather use templates directly within a view callable (without the indirection of using ``renderer`` in view configuration), see the functions in :mod:`pyramid.renderers` for APIs which allow you to render templates imperatively. Template variables provided by Pyramid -------------------------------------- Pyramid by default will provide a set of variables that are available within your templates, please see :ref:`renderer_system_values` for more information about those variables. Using a Chameleon macro name within a renderer name --------------------------------------------------- At times, you may want to render a macro inside of a Chameleon ZPT template instead of the full Chameleon ZPT template. To render the content of a ``define-macro`` field inside a Chameleon ZPT template, given a Chameleon template file named ``foo.pt`` and a macro named ``bar`` defined within it (e.g. ``
...
``), you can configure the template as a :term:`renderer` like so: .. code-block:: python :linenos: from pyramid.view import view_config @view_config(renderer='foo#bar.pt') def my_view(request): return {'project':'my project'} The above will render only the ``bar`` macro defined within the ``foo.pt`` template instead of the entire template. .. index:: single: template renderer side effects Side effects of rendering a Chameleon template ---------------------------------------------- When a Chameleon template is rendered from a file, the templating engine writes a file in the same directory as the template file itself as a kind of cache, in order to do less work the next time the template needs to be read from disk. If you see "strange" ``.py`` files showing up in your ``templates`` directory (or otherwise directly "next" to your templates), it is due to this feature. If you're using a version control system such as Subversion, you should configure it to ignore these files. Here's the contents of the author's ``svn propedit svn:ignore .`` in each of my ``templates`` directories. .. code-block:: text *.pt.py *.txt.py Note that I always name my Chameleon ZPT template files with a ``.pt`` extension and my Chameleon text template files with a ``.txt`` extension so that these ``svn:ignore`` patterns work. .. index:: pair: debugging; templates .. _debug_templates_section: Nicer exceptions in Chameleon templates --------------------------------------- The exceptions raised by Chameleon templates when a rendering fails are sometimes less than helpful. :app:`Pyramid` allows you to configure your application development environment so that exceptions generated by Chameleon during template compilation and execution will contain nicer debugging information. .. warning:: Template-debugging behavior is not recommended for production sites as it slows renderings; it's usually only desirable during development. In order to turn on template exception debugging, you can use an environment variable setting or a configuration file setting. To use an environment variable, start your application under a shell using the ``PYRAMID_DEBUG_TEMPLATES`` operating system environment variable set to ``1``, For example: .. code-block:: text $ PYRAMID_DEBUG_TEMPLATES=1 bin/pserve myproject.ini To use a setting in the application ``.ini`` file for the same purpose, set the ``pyramid.debug_templates`` key to ``true`` within the application's configuration section, e.g.: .. code-block:: ini :linenos: [app:main] use = egg:MyProject pyramid.debug_templates = true With template debugging off, a :exc:`NameError` exception resulting from rendering a template with an undefined variable (e.g. ``${wrong}``) might end like this: .. code-block:: text File "...", in __getitem__ raise NameError(key) NameError: wrong Note that the exception has no information about which template was being rendered when the error occurred. But with template debugging on, an exception resulting from the same problem might end like so: .. code-block:: text RuntimeError: Caught exception rendering template. - Expression: ``wrong`` - Filename: /home/fred/env/proj/proj/templates/mytemplate.pt - Arguments: renderer_name: proj:templates/mytemplate.pt template: xincludes: request: project: proj macros: context: view: NameError: wrong The latter tells you which template the error occurred in, as well as displaying the arguments passed to the template itself. .. note:: Turning on ``pyramid.debug_templates`` has the same effect as using the Chameleon environment variable ``CHAMELEON_DEBUG``. See `Chameleon Configuration `_ for more information. .. index:: single: automatic reloading of templates single: template automatic reload .. _reload_templates_section: Automatically reloading templates --------------------------------- It's often convenient to see changes you make to a template file appear immediately without needing to restart the application process. :app:`Pyramid` allows you to configure your application development environment so that a change to a template will be automatically detected, and the template will be reloaded on the next rendering. .. warning:: Auto-template-reload behavior is not recommended for production sites as it slows rendering slightly; it's usually only desirable during development. In order to turn on automatic reloading of templates, you can use an environment variable, or a configuration file setting. To use an environment variable, start your application under a shell using the ``PYRAMID_RELOAD_TEMPLATES`` operating system environment variable set to ``1``, For example: .. code-block:: text $ PYRAMID_RELOAD_TEMPLATES=1 bin/pserve myproject.ini To use a setting in the application ``.ini`` file for the same purpose, set the ``pyramid.reload_templates`` key to ``true`` within the application's configuration section, e.g.: .. code-block:: ini :linenos: [app:main] use = egg:MyProject pyramid.reload_templates = true Settings -------- Chameleon derives additional settings to configure its template renderer. Many of these settings are optional and only need to be set if they should be different from the default. The below values can be present in the ``.ini`` file used to configure the Pyramid application (in the ``app`` section representing your Pyramid app) or they can be passed directly within the ``settings`` argument passed to a Pyramid Configurator. ``pyramid.reload_templates`` ``true`` or ``false`` representing whether Chameleon templates should be reloaded when they change on disk. Useful for development to be ``true``. ``pyramid.debug_templates`` ``true`` or ``false`` representing whether Chameleon templates should be have extra debugging info turned on in tracebacks it generates. Changing the Content-Type of a Chameleon-rendered response ---------------------------------------------------------- Here's an example of changing the content-type and status of the response object returned by a Chameleon-rendered Pyramid view: .. code-block:: python :linenos: @view_config(renderer='foo.pt') def sample_view(request): request.response.content_type = 'text/plain' response.status_int = 204 return response See :ref:`request_response_attr` for more information. .. index:: single: template internationalization single: internationalization (of templates) Chameleon template internationalization --------------------------------------- Chameleon supports internationalized units of text by reusing the translation facilities provided within Pyramid. See :ref:`i18n_chapter` for a general description of these facilities. Translating template content ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You need to add a few boilerplate lines to your application's ``setup.py`` file in order to properly generate :term:`gettext` files from your application's templates. .. note:: See :ref:`project_narr` to learn about the composition of an application's ``setup.py`` file. In particular, add the ``Babel`` and ``lingua`` distributions to the ``install_requires`` list and insert a set of references to :term:`Babel` *message extractors* within the call to :func:`setuptools.setup` inside your application's ``setup.py`` file: .. code-block:: python :linenos: setup(name="mypackage", # ... install_requires = [ # ... 'Babel', 'lingua', ], message_extractors = { '.': [ ('**.py', 'lingua_python', None ), ('**.pt', 'lingua_xml', None ), ]}, ) The ``message_extractors`` stanza placed into the ``setup.py`` file causes the Babel message catalog extraction machinery to also consider ``*.pt`` files when doing message id extraction. Once this is done you can generate ``.pot`` files derived from your Chameleon templates (and Python code). See :ref:`extracting_messages` in the Pyramid documentation for general information about this. Chameleon template support for translation strings ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When a Pyramid "translation string" (see :ref:`i18n_chapter`) is used as the subject of textual rendering by a ``pyramid_chameleon`` template renderer, it will automatically be translated to the requesting user's language if a suitable translation exists. This is true of both the ZPT and text variants of the Chameleon template renderers. For example, in a Chameleon ZPT template, the translation string represented by "some_translation_string" in each example below will go through translation before being rendered: .. code-block:: xml .. code-block:: xml .. code-block:: xml ${some_translation_string} .. code-block:: xml Click here The features represented by attributes of the ``i18n`` namespace of Chameleon will also consult the :app:`Pyramid` translations. See :ref:`i18n`. .. note:: Unlike when Chameleon is used outside of :app:`Pyramid`, when it is used *within* :app:`Pyramid`, it does not support use of the ``zope.i18n`` translation framework. Applications which use :app:`Pyramid` should use the features documented in this chapter rather than ``zope.i18n``. You can always disuse this automatic translation and perform a more manual translation as described in :ref:`performing_a_translation`. Unit testing ------------ When you are running unit tests, you will be required to use ``config.include('pyramid_chameleon')`` to add ``pyramid_chameleon`` so that its renderers are added to the config and can be used.:: from pyramid import testing from pyramid.response import Response from pyramid.renderers import render # The view we want to test def some_view(request): return Response(render('mypkg:templates/home.pt', {'var': 'testing'})) class TestViews(unittest.TestCase): def setUp(self): self.config = testing.setUp() self.config.include('pyramid_chameleon') def tearDown(self): testing.tearDown() def test_some_view(self): from pyramid.testing import DummyRequest request = DummyRequest() response = some_view(request) # templates/home.pt starts with the standard tag for HTML5 self.assertTrue('`` option with an integer specifying the number of parallel jobs to run on a multiprocessor computer. With the ``--jobs`` option, the duration of compilation can be reduced by about one-third in projects with over 300 templates, as in this example using ``time``. This is executed as follows: .. code-block:: bash $ time pyramid-chameleon-precompile --dir ~/template_files --jobs 1 --cache-dir ~/tmp_chameleoncache INFO:root:Compiled 318 out of 318 found templates 63.78s user 1.04s system 92% cpu 1:09.71 total $ rm -rf ~/tmp_chameleoncache/* $ time CHAMELEON_CACHE=~/tmp_chameleoncache pyramid-chameleon-precompile --dir ~/template_files --jobs 2 --cache-dir ~/tmp_chameleoncache INFO:root:Compiled 318 out of 318 found templates 78.24s user 1.07s system 172% cpu 45.959 total More information ================ .. toctree:: :maxdepth: 1 glossary.rst api.rst Reporting bugs / development versions ===================================== Visit https://github.com/Pylons/pyramid_chameleon to download development or tagged versions. Visit https://github.com/Pylons/pyramid_chameleon/issues to report bugs. Indices and tables ------------------ * :ref:`glossary` * :ref:`genindex` * :ref:`modindex` * :ref:`search`