pyramid 1.4b1

Support and Documentation

See the Pylons Project website to view documentation, report bugs, and obtain support.

License

Pyramid is offered under the BSD-derived Repoze Public License.

Authors

Pyramid is made available by Agendaless Consulting and a team of contributors.

Features

• Small microspeed enhancement which anticipates that a pyramid.response.Response object is likely to be returned from a view. Some code is shortcut if the class of the object returned by a view is this class. A similar microoptimization was done to pyramid.request.Request.is_response.

• Make it possible to use variable arguments on p* commands (pserve, pshell, pviews, etc) in the form a=1 b=2 so you can fill in values in parameterized .ini file, e.g. pshell etc/development.ini http_port=8080. See https://github.com/Pylons/pyramid/pull/714

• A somewhat advanced and obscure feature of Pyramid event handlers is their ability to handle “multi-interface” notifications. These notifications have traditionally presented multiple objects to the subscriber callable. For instance, if an event was sent by code like this:

  registry.notify(event, context)

  In the past, in order to catch such an event, you were obligated to write and register an event subscriber that mentioned both the event and the context in its argument list:

  @subscriber([SomeEvent, SomeContextType])
  def asubscriber(event, context):
      pass

  In many subscriber callables registered this way, it was common for the logic in the subscriber callable to completely ignore the second and following arguments (e.g. context in the above example might be ignored), because they usually existed as attributes of the event anyway. You could usually get the same value by doing event.context or similar.

  The fact that you needed to put an extra argument which you usually ignored in the subscriber callable body was only a minor annoyance until we added “subscriber predicates”, used to narrow the set of circumstances under which a subscriber will be executed, in a prior 1.4 alpha release. Once those were added, the annoyance was escalated, because subscriber predicates needed to accept the same argument list and arity as the subscriber callables that they were configured against. So, for example, if you had these two subscriber registrations in your code:

  @subscriber([SomeEvent, SomeContextType])
  def asubscriber(event, context):
      pass
  
  @subscriber(SomeOtherEvent)
  def asubscriber(event):
      pass

  And you wanted to use a subscriber predicate:

  @subscriber([SomeEvent, SomeContextType], mypredicate=True)
  def asubscriber1(event, context):
      pass
  
  @subscriber(SomeOtherEvent, mypredicate=True)
  def asubscriber2(event):
      pass

  If an existing mypredicate subscriber predicate had been written in such a way that it accepted only one argument in its __call__, you could not use it against a subscription which named more than one interface in its subscriber interface list. Similarly, if you had written a subscriber predicate that accepted two arguments, you couldn’t use it against a registration that named only a single interface type.

  For example, if you created this predicate:

  class MyPredicate(object):
      # portions elided...
      def __call__(self, event):
          return self.val == event.context.foo

  It would not work against a multi-interface-registered subscription, so in the above example, when you attempted to use it against asubscriber1, it would fail at runtime with a TypeError, claiming something was attempting to call it with too many arguments.

  To hack around this limitation, you were obligated to design the mypredicate predicate to expect to receive in its __call__ either a single event argument (a SomeOtherEvent object) or a pair of arguments (a SomeEvent object and a SomeContextType object), presumably by doing something like this:

  class MyPredicate(object):
      # portions elided...
      def __call__(self, event, context=None):
          return self.val == event.context.foo

  This was confusing and bad.

  In order to allow people to ignore unused arguments to subscriber callables and to normalize the relationship between event subscribers and subscriber predicates, we now allow both subscribers and subscriber predicates to accept only a single event argument even if they’ve been subscribed for notifications that involve multiple interfaces. Subscribers and subscriber predicates that accept only one argument will receive the first object passed to notify; this is typically (but not always) the event object. The other objects involved in the subscription lookup will be discarded. You can now write an event subscriber that accepts only event even if it subscribes to multiple interfaces:

  @subscriber([SomeEvent, SomeContextType])
  def asubscriber(event):
      # this will work!

  This prevents you from needing to match the subscriber callable parameters to the subscription type unnecessarily, especially when you don’t make use of any argument in your subscribers except for the event object itself.

  Note, however, that if the event object is not the first object in the call to notify, you’ll run into trouble. For example, if notify is called with the context argument first:

  registry.notify(context, event)

  You won’t be able to take advantage of the event-only feature. It will “work”, but the object received by your event handler won’t be the event object, it will be the context object, which won’t be very useful:

  @subscriber([SomeContextType, SomeEvent])
  def asubscriber(event):
      # bzzt! you'll be getting the context here as ``event``, and it'll
      # be useless

  Existing multiple-argument subscribers continue to work without issue, so you should continue use those if your system notifies using multiple interfaces and the first interface is not the event interface. For example:

  @subscriber([SomeContextType, SomeEvent])
  def asubscriber(context, event):
      # this will still work!

  The event-only feature makes it possible to use a subscriber predicate that accepts only a request argument within both multiple-interface subscriber registrations and single-interface subscriber registrations. You needn’t make slightly different variations of predicates depending on the subscription type arguments. Instead, just write all your subscriber predicates so they only accept event in their __call__ and they’ll be useful across all registrations for subscriptions that use an event as their first argument, even ones which accept more than just event.

  However, the same caveat applies to predicates as to subscriber callables: if you’re subscribing to a multi-interface event, and the first interface is not the event interface, the predicate won’t work properly. In such a case, you’ll need to match the predicate __call__ argument ordering and composition to the ordering of the interfaces. For example, if the registration for the subscription uses [SomeContext, SomeEvent], you’ll need to reflect that in the ordering of the parameters of the predicate’s __call__ method:

  def __call__(self, context, event):
      return event.request.path.startswith(self.val)

  tl;dr: 1) When using multi-interface subscriptions, always use the event type as the first subscription registration argument and 2) When 1 is true, use only event in your subscriber and subscriber predicate parameter lists, no matter how many interfaces the subscriber is notified with. This combination will result in the maximum amount of reusability of subscriber predicates and the least amount of thought on your part. Drink responsibly.

Bug Fixes

• A failure when trying to locate the attribute __text__ on route and view predicates existed when the debug_routematch setting was true or when the pviews command was used. See https://github.com/Pylons/pyramid/pull/727

Documentation

• Sync up tutorial source files with the files that are rendered by the scaffold that each uses.

Features

• pyramid.authentication.AuthTktAuthenticationPolicy has been updated to support newer hashing algorithms such as sha512. Existing applications should consider updating if possible for improved security over the default md5 hashing.

• Added an effective_principals route and view predicate.

• Do not allow the userid returned from the authenticated_userid or the userid that is one of the list of principals returned by effective_principals to be either of the strings system.Everyone or system.Authenticated when any of the built-in authorization policies that live in pyramid.authentication are in use. These two strings are reserved for internal usage by Pyramid and they will not be accepted as valid userids.

• Slightly better debug logging from pyramid.authentication.RepozeWho1AuthenticationPolicy.

• pyramid.security.view_execution_permitted used to return True if no view could be found. It now raises a TypeError exception in that case, as it doesn’t make sense to assert that a nonexistent view is execution-permitted. See https://github.com/Pylons/pyramid/issues/299.

• Allow a _depth argument to pyramid.view.view_config, which will permit limited composition reuse of the decorator by other software that wants to provide custom decorators that are much like view_config.

• Allow an iterable of decorators to be passed to pyramid.config.Configurator.add_view. This allows views to be wrapped by more than one decorator without requiring combining the decorators yourself.

Bug Fixes

• In the past if a renderer returned None, the body of the resulting response would be set explicitly to the empty string. Instead, now, the body is left unchanged, which allows the renderer to set a body itself by using e.g. request.response.body = b'foo'. The body set by the renderer will be unmolested on the way out. See https://github.com/Pylons/pyramid/issues/709

• In uncommon cases, the pyramid_excview_tween_factory might have inadvertently raised a KeyError looking for request_iface as an attribute of the request. It no longer fails in this case. See https://github.com/Pylons/pyramid/issues/700

• Be more tolerant of potential error conditions in match_param and physical_path predicate implementations; instead of raising an exception, return False.

• pyramid.view.render_view was not functioning properly under Python 3.x due to a byte/unicode discrepancy. See http://github.com/Pylons/pyramid/issues/721

Deprecations

• pyramid.authentication.AuthTktAuthenticationPolicy will emit a warning if an application is using the policy without explicitly passing a hashalg argument. This is because the default is “md5” which is considered theoretically subject to collision attacks. If you really want “md5” then you must specify it explicitly to get rid of the warning.

Documentation

• All of the tutorials that use pyramid.authentication.AuthTktAuthenticationPolicy now explicitly pass sha512 as a hashalg argument.

Internals

• Move TopologicalSorter from pyramid.config.util to pyramid.util, move CyclicDependencyError from pyramid.config.util to pyramid.exceptions, rename Singleton to Sentinel and move from pyramid.config.util to pyramid.util; this is in an effort to move that stuff that may be an API one day out of pyramid.config.util, because that package should never be imported from non-Pyramid code. TopologicalSorter is still not an API, but may become one.

• Get rid of shady monkeypatching of pyramid.request.Request and pyramid.response.Response done within the __init__.py of Pyramid. Webob no longer relies on this being done. Instead, the ResponseClass attribute of the Pyramid Request class is assigned to the Pyramid response class; that’s enough to satisfy WebOb and behave as it did before with the monkeypatching.

Bug Fixes

• The match_param predicate’s text method was fixed to sort its values. Part of https://github.com/Pylons/pyramid/pull/705

• 1.4a pyramid.scripting.prepare behaved differently than 1.3 series function of same name. In particular, if passed a request, it would not set the registry attribute of the request like 1.3 did. A symptom would be that passing a request to pyramid.paster.bootstrap (which uses the function) that did not have a registry attribute could assume that the registry would be attached to the request by Pyramid. This assumption could be made in 1.3, but not in 1.4. The assumption can now be made in 1.4 too (a registry is attached to a request passed to bootstrap or prepare).

• When registering a view configuration that named a Chameleon ZPT renderer with a macro name in it (e.g. renderer='some/template#somemacro.pt) as well as a view configuration without a macro name it it that pointed to the same template (e.g. renderer='some/template.pt'), internal caching could confuse the two, and your code might have rendered one instead of the other.

Features

• Allow multiple values to be specified to the request_param view/route predicate as a sequence. Previously only a single string value was allowed. See https://github.com/Pylons/pyramid/pull/705

• Comments with references to documentation sections placed in scaffold .ini files.

• Added an HTTP Basic authentication policy at pyramid.authentication.BasicAuthAuthenticationPolicy.

• The Configurator testing_securitypolicy method now returns the policy object it creates.

• The Configurator testing_securitypolicy method accepts two new arguments: remember_result and forget_result. If supplied, these values influence the result of the policy’s remember and forget methods, respectively.

• The DummySecurityPolicy created by testing_securitypolicy now sets a forgotten value on the policy (the value True) when its forget method is called.

• The DummySecurityPolicy created by testing_securitypolicy now sets a remembered value on the policy, which is the value of the principal argument it’s called with when its remember method is called.

• New physical_path view predicate. If specified, this value should be a string or a tuple representing the physical traversal path of the context found via traversal for this predicate to match as true. For example: physical_path='/' or physical_path='/a/b/c' or physical_path=('', 'a', 'b', 'c'). This is not a path prefix match or a regex, it’s a whole-path match. It’s useful when you want to always potentially show a view when some object is traversed to, but you can’t be sure about what kind of object it will be, so you can’t use the context predicate. The individual path elements inbetween slash characters or in tuple elements should be the Unicode representation of the name of the resource and should not be encoded in any way.

Bug Fixes

• When trying to determine Mako defnames and Chameleon macro names in asset specifications, take into account that the filename may have a hyphen in it. See https://github.com/Pylons/pyramid/pull/692

Features

• A new pyramid.session.check_csrf_token convenience function was added.

• A check_csrf view predicate was added. For example, you can now do config.add_view(someview, check_csrf=True). When the predicate is checked, if the csrf_token value in request.params matches the CSRF token in the request’s session, the view will be permitted to execute. Otherwise, it will not be permitted to execute.

• Add Base.metadata.bind = engine to alchemy template, so that tables defined imperatively will work.

Documentation

• update wiki2 SQLA tutorial with the changes required after inserting Base.metadata.bind = engine into the alchemy scaffold.

Bug Fixes

• Forward port from 1.3 branch: When no authentication policy was configured, a call to pyramid.security.effective_principals would unconditionally return the empty list. This was incorrect, it should have unconditionally returned [Everyone], and now does.

• Explicit url dispatch regexes can now contain colons. https://github.com/Pylons/pyramid/issues/629

• On at least one 64-bit Ubuntu system under Python 3.2, using the view_config decorator caused a RuntimeError: dictionary changed size during iteration exception. It no longer does. See https://github.com/Pylons/pyramid/issues/635 for more information.

• In Mako Templates lookup, check if the uri is already adjusted and bring it back to an asset spec. Normally occurs with inherited templates or included components. https://github.com/Pylons/pyramid/issues/606 https://github.com/Pylons/pyramid/issues/607

• In Mako Templates lookup, check for absolute uri (using mako directories) when mixing up inheritance with asset specs. https://github.com/Pylons/pyramid/issues/662

• HTTP Accept headers were not being normalized causing potentially conflicting view registrations to go unnoticed. Two views that only differ in the case (‘text/html’ vs. ‘text/HTML’) will now raise an error. https://github.com/Pylons/pyramid/pull/620

• Forward-port from 1.3 branch: when registering multiple views with an accept predicate in a Pyramid application runing under Python 3, you might have received a TypeError: unorderable types: function() < function() exception.

Features

• Configurator.add_directive now accepts arbitrary callables like partials or objects implementing __call__ which dont have __name__ and __doc__ attributes. See https://github.com/Pylons/pyramid/issues/621 and https://github.com/Pylons/pyramid/pull/647.

• Third-party custom view, route, and subscriber predicates can now be added for use by view authors via pyramid.config.Configurator.add_view_predicate, pyramid.config.Configurator.add_route_predicate and pyramid.config.Configurator.add_subscriber_predicate. So, for example, doing this:

  config.add_view_predicate('abc', my.package.ABCPredicate)

  Might allow a view author to do this in an application that configured that predicate:

  @view_config(abc=1)

  Similar features exist for add_route, and add_subscriber. See “Adding A Third Party View, Route, or Subscriber Predicate” in the Hooks chapter for more information.

  Note that changes made to support the above feature now means that only actions registered using the same “order” can conflict with one another. It used to be the case that actions registered at different orders could potentially conflict, but to my knowledge nothing ever depended on this behavior (it was a bit silly).

• Custom objects can be made easily JSON-serializable in Pyramid by defining a __json__ method on the object’s class. This method should return values natively serializable by json.dumps (such as ints, lists, dictionaries, strings, and so forth).

• The JSON renderer now allows for the definition of custom type adapters to convert unknown objects to JSON serializations.

• As of this release, the request_method predicate, when used, will also imply that HEAD is implied when you use GET. For example, using @view_config(request_method='GET') is equivalent to using @view_config(request_method=('GET', 'HEAD')). Using @view_config(request_method=('GET', 'POST') is equivalent to using @view_config(request_method=('GET', 'HEAD', 'POST'). This is because HEAD is a variant of GET that omits the body, and WebOb has special support to return an empty body when a HEAD is used.

• config.add_request_method has been introduced to support extending request objects with arbitrary callables. This method expands on the previous config.set_request_property by supporting methods as well as properties. This method now causes less code to be executed at request construction time than config.set_request_property in version 1.3.

• Don’t add a ? to URLs generated by request.resource_url if the query argument is provided but empty.

• Don’t add a ? to URLs generated by request.route_url if the _query argument is provided but empty.

• The static view machinery now raises (rather than returns) HTTPNotFound and HTTPMovedPermanently exceptions, so these can be caught by the NotFound view (and other exception views).

• The Mako renderer now supports a def name in an asset spec. When the def name is present in the asset spec, the system will render the template def within the template and will return the result. An example asset spec is package:path/to/template#defname.mako. This will render the def named defname inside the template.mako template instead of rendering the entire template. The old way of returning a tuple in the form ('defname', {}) from the view is supported for backward compatibility,

• The Chameleon ZPT renderer now accepts a macro name in an asset spec. When the macro name is present in the asset spec, the system will render the macro listed as a define-macro and return the result instead of rendering the entire template. An example asset spec: package:path/to/template#macroname.pt. This will render the macro defined as macroname within the template.pt template instead of the entire templae.

• When there is a predicate mismatch exception (seen when no view matches for a given request due to predicates not working), the exception now contains a textual description of the predicate which didn’t match.

• An add_permission directive method was added to the Configurator. This directive registers a free-standing permission introspectable into the Pyramid introspection system. Frameworks built atop Pyramid can thus use the the permissions introspectable category data to build a comprehensive list of permissions supported by a running system. Before this method was added, permissions were already registered in this introspectable category as a side effect of naming them in an add_view call, this method just makes it possible to arrange for a permission to be put into the permissions introspectable category without naming it along with an associated view. Here’s an example of usage of add_permission:

  config = Configurator()
  config.add_permission('view')

• The UnencryptedCookieSessionFactoryConfig now accepts signed_serialize and signed_deserialize hooks which may be used to influence how the sessions are marshalled (by default this is done with HMAC+pickle).

• pyramid.testing.DummyRequest now supports methods supplied by the pyramid.util.InstancePropertyMixin class such as set_property.

• Request properties and methods added via config.set_request_property or config.add_request_method are now available to tweens.

• Request properties and methods added via config.set_request_property or config.add_request_method are now available in the request object returned from pyramid.paster.bootstrap.

• request.context of environment request during bootstrap is now the root object if a context isn’t already set on a provided request.

• The pyramid.decorator.reify function is now an API, and was added to the API documentation.

• Added the pyramid.testing.testConfig context manager, which can be used to generate a configurator in a test, e.g. with testing.testConfig(...):.

• Users can now invoke a subrequest from within view code using a new request.invoke_subrequest API.

Deprecations

• The pyramid.config.Configurator.set_request_property has been documentation-deprecated. The method remains usable but the more featureful pyramid.config.Configurator.add_request_method should be used in its place (it has all of the same capabilities but can also extend the request object with methods).

Backwards Incompatibilities

• The Pyramid router no longer adds the values bfg.routes.route or bfg.routes.matchdict to the request’s WSGI environment dictionary. These values were docs-deprecated in repoze.bfg 1.0 (effectively seven minor releases ago). If your code depended on these values, use request.matched_route and request.matchdict instead.

• It is no longer possible to pass an environ dictionary directly to pyramid.traversal.ResourceTreeTraverser.__call__ (aka ModelGraphTraverser.__call__). Instead, you must pass a request object. Passing an environment instead of a request has generated a deprecation warning since Pyramid 1.1.

• Pyramid will no longer work properly if you use the webob.request.LegacyRequest as a request factory. Instances of the LegacyRequest class have a request.path_info which return a string. This Pyramid release assumes that request.path_info will unconditionally be Unicode.

• The functions from pyramid.chameleon_zpt and pyramid.chameleon_text named get_renderer, get_template, render_template, and render_template_to_response have been removed. These have issued a deprecation warning upon import since Pyramid 1.0. Use pyramid.renderers.get_renderer(), pyramid.renderers.get_renderer().implementation(), pyramid.renderers.render() or pyramid.renderers.render_to_response respectively instead of these functions.

• The pyramid.configuration module was removed. It had been deprecated since Pyramid 1.0 and printed a deprecation warning upon its use. Use pyramid.config instead.

• The pyramid.paster.PyramidTemplate API was removed. It had been deprecated since Pyramid 1.1 and issued a warning on import. If your code depended on this, adjust your code to import pyramid.scaffolds.PyramidTemplate instead.

• The pyramid.settings.get_settings() API was removed. It had been printing a deprecation warning since Pyramid 1.0. If your code depended on this API, use pyramid.threadlocal.get_current_registry().settings instead or use the settings attribute of the registry available from the request (request.registry.settings).

• These APIs from the pyramid.testing module were removed. They have been printing deprecation warnings since Pyramid 1.0:

  • registerDummySecurityPolicy, use pyramid.config.Configurator.testing_securitypolicy instead.

  • registerResources (aka registerModels, use pyramid.config.Configurator.testing_resources instead.

  • registerEventListener, use pyramid.config.Configurator.testing_add_subscriber instead.

  • registerTemplateRenderer (aka registerDummyRenderer`), use pyramid.config.Configurator.testing_add_template instead.

  • registerView, use pyramid.config.Configurator.add_view instead.

  • registerUtility, use pyramid.config.Configurator.registry.registerUtility instead.

  • registerAdapter, use pyramid.config.Configurator.registry.registerAdapter instead.

  • registerSubscriber, use pyramid.config.Configurator.add_subscriber instead.

  • registerRoute, use pyramid.config.Configurator.add_route instead.

  • registerSettings, use pyramid.config.Configurator.add_settings instead.

• In Pyramid 1.3 and previous, the __call__ method of a Response object was invoked before any finished callbacks were executed. As of this release, the __call__ method of a Response object is invoked after finished callbacks are executed. This is in support of the request.invoke_subrequest feature.

Documentation

• Added an “Upgrading Pyramid” chapter to the narrative documentation. It describes how to cope with deprecations and removals of Pyramid APIs and how to show Pyramid-generated deprecation warnings while running tests and while running a server.

• Added a “Invoking a Subrequest” chapter to the documentation. It describes how to use the new request.invoke_subrequest API.

Dependencies

• Pyramid now requires WebOb 1.2b3+ (the prior Pyramid release only relied on 1.2dev+). This is to ensure that we obtain a version of WebOb that returns request.path_info as text.