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What's New in Pyramid 1.5

This article explains the new features in :app:`Pyramid` version 1.5 as compared to its predecessor, :app:`Pyramid` 1.4. It also documents backwards incompatibilities between the two versions and deprecations added to :app:`Pyramid` 1.5, as well as software dependency changes and notable documentation additions.

Major Backwards Incompatibilities

  • Pyramid no longer depends on or configures the Mako and Chameleon templating system renderers by default. Disincluding these templating systems by default means that the Pyramid core has fewer dependencies and can run on future platforms without immediate concern for the compatibility of its templating add-ons. It also makes maintenance slightly more effective, as different people can maintain the templating system add-ons that they understand and care about without needing commit access to the Pyramid core, and it allows users who just don't want to see any packages they don't use come along for the ride when they install Pyramid.

    This means that upon upgrading to Pyramid 1.5a2+, projects that use either of these templating systems will see a traceback that ends something like this when their application attempts to render a Chameleon or Mako template:

    ValueError: No such renderer factory .pt

    Or:

    ValueError: No such renderer factory .mako

    Or:

    ValueError: No such renderer factory .mak

    Support for Mako templating has been moved into an add-on package named pyramid_mako, and support for Chameleon templating has been moved into an add-on package named pyramid_chameleon. These packages are drop-in replacements for the old built-in support for these templating langauges. All you have to do is install them and make them active in your configuration to register renderer factories for .pt and/or .mako (or .mak) to make your application work again.

    To re-add support for Chameleon and/or Mako template renderers into your existing projects, follow the below steps.

    If you depend on Mako templates:

    • Make sure the pyramid_mako package is installed. One way to do this is by adding pyramid_mako to the install_requires section of your package's setup.py file and afterwards rerunning setup.py develop:

      setup(
    #...
    install_requires=[
        'pyramid_mako',         # new dependency
        'pyramid',
        #...
    ],
)

    • Within the portion of your application which instantiates a Pyramid :class:`~pyramid.config.Configurator` (often the main() function in your project's __init__.py file), tell Pyramid to include the pyramid_mako includeme:

      config = Configurator(.....)
config.include('pyramid_mako')

    If you depend on Chameleon templates:

    • Make sure the pyramid_chameleon package is installed. One way to do this is by adding pyramid_chameleon to the install_requires section of your package's setup.py file and afterwards rerunning setup.py develop:

      setup(
    #...
    install_requires=[
        'pyramid_chameleon',         # new dependency
        'pyramid',
        #...
    ],
)

    • Within the portion of your application which instantiates a Pyramid :class:`~pyramid.config.Configurator` (often the main() function in your project's __init__.py file), tell Pyramid to include the pyramid_chameleon includeme:

      config = Configurator(.....)
config.include('pyramid_chameleon')

    Note that it's also fine to install these packages into older Pyramids for forward compatibility purposes. Even if you don't upgrade to Pyramid 1.5 immediately, performing the above steps in a Pyramid 1.4 installation is perfectly fine, won't cause any difference, and will give you forward compatibility when you eventually do upgrade to Pyramid 1.5.

    With the removal of Mako and Chameleon support from the core, some unit tests that use the pyramid.renderers.render* methods may begin to fail. If any of your unit tests are invoking either pyramid.renderers.render() or pyramid.renderers.render_to_response() with either Mako or Chameleon templates then the pyramid.config.Configurator instance in effect during the unit test should be also be updated to include the addons, as shown above. For example:

    class ATest(unittest.TestCase):
    def setUp(self):
        self.config = pyramid.testing.setUp()
        self.config.include('pyramid_mako')

    def test_it(self):
        result = pyramid.renderers.render('mypkg:templates/home.mako', {})

    Or:

    class ATest(unittest.TestCase):
    def setUp(self):
        self.config = pyramid.testing.setUp()
        self.config.include('pyramid_chameleon')

    def test_it(self):
        result = pyramid.renderers.render('mypkg:templates/home.pt', {})

  • If you're using the Pyramid debug toolbar, when you upgrade Pyramid to 1.5a2+, you'll also need to upgrade the pyramid_debugtoolbar package to at least version 1.0.8, as older toolbar versions are not compatible with Pyramid 1.5a2+ due to the removal of Mako support from the core. It's fine to use this newer version of the toolbar code with older Pyramids too.

Feature Additions

The feature additions in Pyramid 1.5 follow.

  • Python 3.4 compatibility.

  • Add pdistreport script, which prints the Python version in use, the Pyramid version in use, and the version number and location of all Python distributions currently installed.

  • Add the ability to invert the result of any view, route, or subscriber predicate value using the not_ class. For example:

    from pyramid.config import not_

@view_config(route_name='myroute', request_method=not_('POST'))
def myview(request): ...

    The above example will ensure that the view is called if the request method is not POST, at least if no other view is more specific.

    The :class:`pyramid.config.not_` class can be used against any value that is a predicate value passed in any of these contexts:

  • View lookup will now search for valid views based on the inheritance hierarchy of the context. It tries to find views based on the most specific context first, and upon predicate failure, will move up the inheritance chain to test views found by the super-type of the context. In the past, only the most specific type containing views would be checked and if no matching view could be found then a PredicateMismatch would be raised. Now predicate mismatches don't hide valid views registered on super-types. Here's an example that now works:

    class IResource(Interface):

    ...

@view_config(context=IResource)
def get(context, request):

    ...

@view_config(context=IResource, request_method='POST')
def post(context, request):

    ...

@view_config(context=IResource, request_method='DELETE')
def delete(context, request):

    ...

@implementer(IResource)
class MyResource:

    ...

@view_config(context=MyResource, request_method='POST')
def override_post(context, request):

    ...

    Previously the override_post view registration would hide the get and delete views in the context of MyResource -- leading to a predicate mismatch error when trying to use GET or DELETE methods. Now the views are found and no predicate mismatch is raised. See Pylons#786 and Pylons#1004 and Pylons#1046

  • scripts/prequest.py (aka the prequest console script): added support for submitting PUT and PATCH requests. See Pylons#1033. add support for submitting OPTIONS and PROPFIND requests, and allow users to specify basic authentication credentials in the request via a --login argument to the script. See Pylons#1039.

  • The :meth:`pyramid.config.Configurator.add_route` method now supports being called with an external URL as pattern. See Pylons#611 and the documentation section :ref:`external_route_narr`.

  • :class:`pyramid.authorization.ACLAuthorizationPolicy` supports __acl__ as a callable. This removes the ambiguity between the potential AttributeError that would be raised on the context when the property was not defined and the AttributeError that could be raised from any user-defined code within a dynamic property. It is recommended to define a dynamic ACL as a callable to avoid this ambiguity. See Pylons#735.

  • Allow a protocol-relative URL (e.g. //example.com/images) to be passed to :meth:`pyramid.config.Configurator.add_static_view`. This allows externally-hosted static URLs to be generated based on the current protocol.

  • The :class:`pyramid.authentication.AuthTktAuthenticationPolicy` class has two new options to configure its domain usage:

    • parent_domain: if set the authentication cookie is set on the parent domain. This is useful if you have multiple sites sharing the same domain.
    • domain: if provided the cookie is always set for this domain, bypassing all usual logic.

    See Pylons#1028, Pylons#1072 and Pylons#1078.

  • The :class:`pyramid.authentication.AuthTktPolicy` now supports IPv6 addresses when using the include_ip=True option. This is possibly incompatible with alternative auth_tkt implementations, as the specification does not define how to properly handle IPv6. See Pylons#831.

  • Make it possible to use variable arguments via :func:`pyramid.paster.get_appsettings`. This also allowed the generated initialize_db script from the alchemy scaffold to grow support for options in the form a=1 b=2 so you can fill in values in a parameterized .ini file, e.g. initialize_myapp_db etc/development.ini a=1 b=2. See Pylons#911

  • The request.session.check_csrf_token() method and the check_csrf view predicate now take into account the value of the HTTP header named X-CSRF-Token (as well as the csrf_token form parameter, which they always did). The header is tried when the form parameter does not exist.

  • You can now generate "hybrid" urldispatch/traversal URLs more easily by using the new route_name, route_kw and route_remainder_name arguments to :meth:`~pyramid.request.Request.resource_url` and :meth:`~pyramid.request.Request.resource_path`. See :ref:`generating_hybrid_urls`.

  • A new http exception superclass named :class:`~pyramid.httpexceptions.HTTPSuccessful` was added. You can use this class as the context of an exception view to catch all 200-series "exceptions" (e.g. "raise HTTPOk"). This also allows you to catch only the :class:`~pyramid.httpexceptions.HTTPOk` exception itself; previously this was impossible because a number of other exceptions (such as HTTPNoContent) inherited from HTTPOk, but now they do not.

  • It is now possible to escape double braces in Pyramid scaffolds (unescaped, these represent replacement values). You can use \{\{a\}\} to represent a "bare" {{a}}. See Pylons#862

  • Add localizer and locale_name properties (reified) to :class:`pyramid.request.Request`. See Pylons#508. Note that the :func:`pyramid.i18n.get_localizer` and :func:`pyramid.i18n.get_locale_name` functions now simply look up these properties on the request.

  • The pserve command now takes a -v (or --verbose) flag and a -q (or --quiet) flag. Output from running pserve can be controlled using these flags. -v can be specified multiple times to increase verbosity. -q sets verbosity to 0 unconditionally. The default verbosity level is 1.

  • The alchemy scaffold tests now provide better coverage. See Pylons#1029

  • Users can now provide dotted Python names to as the factory argument the Configurator methods named :meth:`~pyramid.config.Configurator.add_view_predicate`, :meth:`~pyramid.config.Configurator.add_route_predicate` and :meth:`~pyramid.config.Configurator.add_subscriber_predicate`. Instead of passing the predicate factory directly, you can pass a dotted name which refers to the factory.

  • :func:`pyramid.path.package_name` no longer thows an exception when resolving the package name for namespace packages that have no __file__ attribute.

  • An authorization API has been added as a method of the request: :meth:`pyramid.request.Request.has_permission`. It is a method-based alternative to the :func:`pyramid.security.has_permission` API and works exactly the same. The older API is now deprecated.

  • Property API attributes have been added to the request for easier access to authentication data: :attr:`pyramid.request.Request.authenticated_userid`, :attr:`pyramid.request.Request.unauthenticated_userid`, and :attr:`pyramid.request.Request.effective_principals`. These are analogues, respectively, of :func:`pyramid.security.authenticated_userid`, :func:`pyramid.security.unauthenticated_userid`, and :func:`pyramid.security.effective_principals`. They operate exactly the same, except they are attributes of the request instead of functions accepting a request. They are properties, so they cannot be assigned to. The older function-based APIs are now deprecated.

  • Pyramid's console scripts (pserve, pviews, etc) can now be run directly, allowing custom arguments to be sent to the python interpreter at runtime. For example:

    python -3 -m pyramid.scripts.pserve development.ini

  • Added a specific subclass of :class:`pyramid.httpexceptions.HTTPBadRequest` named :class:`pyramid.exceptions.BadCSRFToken` which will now be raised in response to failures in the check_csrf_token view predicate. See Pylons#1149

  • Added a new SignedCookieSessionFactory which is very similar to the UnencryptedCookieSessionFactoryConfig but with a clearer focus on signing content. The custom serializer arguments to this function should only focus on serializing, unlike its predecessor which required the serializer to also perform signing. See Pylons#1142 . Note that cookies generated using SignedCookieSessionFactory are not compatible with cookies generated using UnencryptedCookieSessionFactory, so existing user session data will be destroyed if you switch to it.

  • Added a new BaseCookieSessionFactory which acts as a generic cookie factory that can be used by framework implementors to create their own session implementations. It provides a reusable API which focuses strictly on providing a dictionary-like object that properly handles renewals, timeouts, and conformance with the ISession API. See Pylons#1142

  • We no longer eagerly clear request.exception and request.exc_info in the exception view tween. This makes it possible to inspect exception information within a finished callback. See Pylons#1223.

Other Backwards Incompatibilities

  • Modified the :meth:`~pyramid.request.Request.current_route_url` method. The method previously returned the URL without the query string by default, it now does attach the query string unless it is overriden.
  • The :meth:`~pyramid.request.Request.route_url` and :meth:`~pyramid.request.Request.route_path` APIs no longer quote / to %2F when a replacement value contains a /. This was pointless, as WSGI servers always unquote the slash anyway, and Pyramid never sees the quoted value.
  • It is no longer possible to set a locale_name attribute of the request, nor is it possible to set a localizer attribute of the request. These are now "reified" properties that look up a locale name and localizer respectively using the machinery described in :ref:`i18n_chapter`.
  • If you send an X-Vhm-Root header with a value that ends with any number of slashes, the trailing slashes will be removed before the URL is generated when you use :meth:`~pyramid.request.Request.resource_url` or :meth:`~pyramid.request.Request.resource_path`. Previously the virtual root path would not have trailing slashes stripped, which would influence URL generation.
  • The :class:`pyramid.interfaces.IResourceURL` interface has now grown two new attributes: virtual_path_tuple and physical_path_tuple. These should be the tuple form of the resource's path (physical and virtual).
  • Removed the request.response_* varying attributes (such as``request.response_headers``) . These attributes had been deprecated since Pyramid 1.1, and as per the deprecation policy, have now been removed.
  • request.response will no longer be mutated when using the :func:`pyramid.renderers.render` API. Almost all renderers mutate the request.response response object (for example, the JSON renderer sets request.response.content_type to application/json), but this is only necessary when the renderer is generating a response; it was a bug when it was done as a side effect of calling :func:`pyramid.renderers.render`.
  • Removed the bfg2pyramid fixer script.
  • The :class:`pyramid.events.NewResponse` event is now sent after response callbacks are executed. It previously executed before response callbacks were executed. Rationale: it's more useful to be able to inspect the response after response callbacks have done their jobs instead of before.
  • Removed the class named pyramid.view.static that had been deprecated since Pyramid 1.1. Instead use :class:`pyramid.static.static_view` with the use_subpath=True argument.
  • Removed the pyramid.view.is_response function that had been deprecated since Pyramid 1.1. Use the :meth:`pyramid.request.Request.is_response` method instead.
  • Removed the ability to pass the following arguments to :meth:`pyramid.config.Configurator.add_route`: view, view_context. view_for, view_permission, view_renderer, and view_attr. Using these arguments had been deprecated since Pyramid 1.1. Instead of passing view-related arguments to add_route, use a separate call to :meth:`pyramid.config.Configurator.add_view` to associate a view with a route using its route_name argument. Note that this impacts the :meth:`pyramid.config.Configurator.add_static_view` function too, because it delegates to``add_route``.
  • Removed the ability to influence and query a :class:`pyramid.request.Request` object as if it were a dictionary. Previously it was possible to use methods like __getitem__, get, items, and other dictlike methods to access values in the WSGI environment. This behavior had been deprecated since Pyramid 1.1. Use methods of request.environ (a real dictionary) instead.
  • Removed ancient backwards compatibility hack in pyramid.traversal.DefaultRootFactory which populated the __dict__ of the factory with the matchdict values for compatibility with BFG 0.9.
  • The renderer_globals_factory argument to the :class:`pyramid.config.Configurator` constructor and the coresponding argument to :meth:`~pyramid.config.Configurator.setup_registry` has been removed. The set_renderer_globals_factory method of :class:`~pyramid.config.Configurator` has also been removed. The (internal) pyramid.interfaces.IRendererGlobals interface was also removed. These arguments, methods and interfaces had been deprecated since 1.1. Use a BeforeRender event subscriber as documented in the "Hooks" chapter of the Pyramid narrative documentation instead of providing renderer globals values to the configurator.
  • The key/values in the _query parameter of :meth:`pyramid.request.Request.route_url` and the query parameter of :meth:`pyramid.request.Request.resource_url` (and their variants), used to encode a value of None as the string 'None', leaving the resulting query string to be a=b&key=None. The value is now dropped in this situation, leaving a query string of a=b&key=. See Pylons#1119

Deprecations

Documentation Enhancements

  • A new documentation chapter named :ref:`quick_tour` was added. It describes starting out with Pyramid from a high level.
  • Added a :ref:`quick_tutorial` to go with the Quick Tour
  • Many other enhancements.

Scaffolding Enhancements

  • All scaffolds have a new HTML + CSS theme.
  • Updated docs and scaffolds to keep in step with new 2.0 release of Lingua. This included removing all setup.cfg files from scaffolds and documentation environments.

Dependency Changes

  • Pyramid no longer depends upon Mako or Chameleon.
  • Pyramid now depends on WebOb>=1.3 (it uses webob.cookies.CookieProfile from 1.3+).