Source code for pyramid.events

import venusian
from zope.interface import Interface, implementer

from pyramid.interfaces import (
    IApplicationCreated,
    IBeforeRender,
    IBeforeTraversal,
    IContextFound,
    INewRequest,
    INewResponse,
)


[docs] class subscriber: """Decorator activated via a :term:`scan` which treats the function being decorated as an event subscriber for the set of interfaces passed as ``*ifaces`` and the set of predicate terms passed as ``**predicates`` to the decorator constructor. For example: .. code-block:: python from pyramid.events import NewRequest from pyramid.events import subscriber @subscriber(NewRequest) def mysubscriber(event): event.request.foo = 1 More than one event type can be passed as a constructor argument. The decorated subscriber will be called for each event type. .. code-block:: python from pyramid.events import NewRequest, NewResponse from pyramid.events import subscriber @subscriber(NewRequest, NewResponse) def mysubscriber(event): print(event) When the ``subscriber`` decorator is used without passing an arguments, the function it decorates is called for every event sent: .. code-block:: python from pyramid.events import subscriber @subscriber() def mysubscriber(event): print(event) This method will have no effect until a :term:`scan` is performed against the package or module which contains it, ala: .. code-block:: python from pyramid.config import Configurator config = Configurator() config.scan('somepackage_containing_subscribers') Any ``**predicate`` arguments will be passed along to :meth:`pyramid.config.Configurator.add_subscriber`. See :ref:`subscriber_predicates` for a description of how predicates can narrow the set of circumstances in which a subscriber will be called. Two additional keyword arguments which will be passed to the :term:`venusian` ``attach`` function are ``_depth`` and ``_category``. ``_depth`` is provided for people who wish to reuse this class from another decorator. The default value is ``0`` and should be specified relative to the ``subscriber`` invocation. It will be passed in to the :term:`venusian` ``attach`` function as the depth of the callstack when Venusian checks if the decorator is being used in a class or module context. It's not often used, but it can be useful in this circumstance. ``_category`` sets the decorator category name. It can be useful in combination with the ``category`` argument of ``scan`` to control which views should be processed. See the :py:func:`venusian.attach` function in Venusian for more information about the ``_depth`` and ``_category`` arguments. .. versionchanged:: 1.9.1 Added the ``_depth`` and ``_category`` arguments. """ venusian = venusian # for unit testing def __init__(self, *ifaces, **predicates): self.ifaces = ifaces self.predicates = predicates self.depth = predicates.pop('_depth', 0) self.category = predicates.pop('_category', 'pyramid') def register(self, scanner, name, wrapped): config = scanner.config for iface in self.ifaces or (Interface,): config.add_subscriber(wrapped, iface, **self.predicates) def __call__(self, wrapped): self.venusian.attach( wrapped, self.register, category=self.category, depth=self.depth + 1, ) return wrapped
[docs] @implementer(INewRequest) class NewRequest: """An instance of this class is emitted as an :term:`event` whenever :app:`Pyramid` begins to process a new request. The event instance has an attribute, ``request``, which is a :term:`request` object. This event class implements the :class:`pyramid.interfaces.INewRequest` interface.""" def __init__(self, request): self.request = request
[docs] @implementer(INewResponse) class NewResponse: """An instance of this class is emitted as an :term:`event` whenever any :app:`Pyramid` :term:`view` or :term:`exception view` returns a :term:`response`. The instance has two attributes:``request``, which is the request which caused the response, and ``response``, which is the response object returned by a view or renderer. If the ``response`` was generated by an :term:`exception view`, the request will have an attribute named ``exception``, which is the exception object which caused the exception view to be executed. If the response was generated by a 'normal' view, this attribute of the request will be ``None``. This event will not be generated if a response cannot be created due to an exception that is not caught by an exception view (no response is created under this circumstace). This class implements the :class:`pyramid.interfaces.INewResponse` interface. .. note:: Postprocessing a response is usually better handled in a WSGI :term:`middleware` component than in subscriber code that is called by a :class:`pyramid.interfaces.INewResponse` event. The :class:`pyramid.interfaces.INewResponse` event exists almost purely for symmetry with the :class:`pyramid.interfaces.INewRequest` event. """ def __init__(self, request, response): self.request = request self.response = response
[docs] @implementer(IBeforeTraversal) class BeforeTraversal: """ An instance of this class is emitted as an :term:`event` after the :app:`Pyramid` :term:`router` has attempted to find a :term:`route` object but before any traversal or view code is executed. The instance has an attribute, ``request``, which is the request object generated by :app:`Pyramid`. Notably, the request object **may** have an attribute named ``matched_route``, which is the matched route if found. If no route matched, this attribute is not available. This class implements the :class:`pyramid.interfaces.IBeforeTraversal` interface. """ def __init__(self, request): self.request = request
[docs] @implementer(IContextFound) class ContextFound: """An instance of this class is emitted as an :term:`event` after the :app:`Pyramid` :term:`router` finds a :term:`context` object (after it performs traversal) but before any view code is executed. The instance has an attribute, ``request``, which is the request object generated by :app:`Pyramid`. Notably, the request object will have an attribute named ``context``, which is the context that will be provided to the view which will eventually be called, as well as other attributes attached by context-finding code. This class implements the :class:`pyramid.interfaces.IContextFound` interface. .. note:: As of :app:`Pyramid` 1.0, for backwards compatibility purposes, this event may also be imported as :class:`pyramid.events.AfterTraversal`. """ def __init__(self, request): self.request = request
AfterTraversal = ContextFound # b/c as of 1.0
[docs] @implementer(IApplicationCreated) class ApplicationCreated: """An instance of this class is emitted as an :term:`event` when the :meth:`pyramid.config.Configurator.make_wsgi_app` is called. The instance has an attribute, ``app``, which is an instance of the :term:`router` that will handle WSGI requests. This class implements the :class:`pyramid.interfaces.IApplicationCreated` interface. .. note:: For backwards compatibility purposes, this class can also be imported as :class:`pyramid.events.WSGIApplicationCreatedEvent`. This was the name of the event class before :app:`Pyramid` 1.0. """ def __init__(self, app): self.app = app self.object = app
WSGIApplicationCreatedEvent = ApplicationCreated # b/c (as of 1.0)
[docs] @implementer(IBeforeRender) class BeforeRender(dict): """ Subscribers to this event may introspect and modify the set of :term:`renderer globals` before they are passed to a :term:`renderer`. This event object itself has a dictionary-like interface that can be used for this purpose. For example:: from pyramid.events import subscriber from pyramid.events import BeforeRender @subscriber(BeforeRender) def add_global(event): event['mykey'] = 'foo' An object of this type is sent as an event just before a :term:`renderer` is invoked. If a subscriber adds a key via ``__setitem__`` that already exists in the renderer globals dictionary, it will overwrite the older value there. This can be problematic because event subscribers to the BeforeRender event do not possess any relative ordering. For maximum interoperability with other third-party subscribers, if you write an event subscriber meant to be used as a BeforeRender subscriber, your subscriber code will need to ensure no value already exists in the renderer globals dictionary before setting an overriding value (which can be done using ``.get`` or ``__contains__`` of the event object). The dictionary returned from the view is accessible through the :attr:`rendering_val` attribute of a :class:`~pyramid.events.BeforeRender` event. Suppose you return ``{'mykey': 'somevalue', 'mykey2': 'somevalue2'}`` from your view callable, like so:: from pyramid.view import view_config @view_config(renderer='some_renderer') def myview(request): return {'mykey': 'somevalue', 'mykey2': 'somevalue2'} :attr:`rendering_val` can be used to access these values from the :class:`~pyramid.events.BeforeRender` object:: from pyramid.events import subscriber from pyramid.events import BeforeRender @subscriber(BeforeRender) def read_return(event): # {'mykey': 'somevalue'} is returned from the view print(event.rendering_val['mykey']) In other words, :attr:`rendering_val` is the (non-system) value returned by a view or passed to ``render*`` as ``value``. This feature is new in Pyramid 1.2. For a description of the values present in the renderer globals dictionary, see :ref:`renderer_system_values`. .. seealso:: See also :class:`pyramid.interfaces.IBeforeRender`. """ def __init__(self, system, rendering_val=None): dict.__init__(self, system) self.rendering_val = rendering_val