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# encoding: utf-8
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"""The IPython Core Notification Center.
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See docs/source/development/notification_blueprint.txt for an overview of the
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notification module.
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"""
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__docformat__ = "restructuredtext en"
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#-----------------------------------------------------------------------------
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# Copyright (C) 2008 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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class NotificationCenter(object):
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"""Synchronous notification center
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Example
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-------
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>>> import IPython.kernel.core.notification as notification
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>>> def callback(theType, theSender, args={}):
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... print theType,theSender,args
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...
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>>> notification.sharedCenter.add_observer(callback, 'NOTIFICATION_TYPE', None)
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>>> notification.sharedCenter.post_notification('NOTIFICATION_TYPE', object()) # doctest:+ELLIPSIS
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NOTIFICATION_TYPE ...
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"""
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def __init__(self):
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super(NotificationCenter, self).__init__()
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self._init_observers()
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def _init_observers(self):
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"""Initialize observer storage"""
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self.registered_types = set() #set of types that are observed
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self.registered_senders = set() #set of senders that are observed
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self.observers = {} #map (type,sender) => callback (callable)
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def post_notification(self, theType, sender, **kwargs):
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"""Post notification (type,sender,**kwargs) to all registered
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observers.
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Implementation
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--------------
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* If no registered observers, performance is O(1).
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* Notificaiton order is undefined.
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* Notifications are posted synchronously.
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"""
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if(theType==None or sender==None):
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raise Exception("NotificationCenter.post_notification requires \
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type and sender.")
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# If there are no registered observers for the type/sender pair
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if((theType not in self.registered_types and
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None not in self.registered_types) or
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(sender not in self.registered_senders and
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None not in self.registered_senders)):
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return
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for o in self._observers_for_notification(theType, sender):
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o(theType, sender, args=kwargs)
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def _observers_for_notification(self, theType, sender):
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"""Find all registered observers that should recieve notification"""
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keys = (
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(theType,sender),
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(theType, None),
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(None, sender),
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(None,None)
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)
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obs = set()
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for k in keys:
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obs.update(self.observers.get(k, set()))
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return obs
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def add_observer(self, callback, theType, sender):
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"""Add an observer callback to this notification center.
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The given callback will be called upon posting of notifications of
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the given type/sender and will receive any additional kwargs passed
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to post_notification.
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Parameters
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----------
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observerCallback : callable
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Callable. Must take at least two arguments::
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observerCallback(type, sender, args={})
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theType : hashable
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The notification type. If None, all notifications from sender
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will be posted.
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sender : hashable
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The notification sender. If None, all notifications of theType
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will be posted.
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"""
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assert(callback != None)
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self.registered_types.add(theType)
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self.registered_senders.add(sender)
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self.observers.setdefault((theType,sender), set()).add(callback)
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def remove_all_observers(self):
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"""Removes all observers from this notification center"""
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self._init_observers()
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sharedCenter = NotificationCenter()
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