/usr/share/pyshared/pyarco/Pattern.py is in atheist 0.20110402-2.
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"""patterns module includes classes and structures of design patterns.
.. moduleauthor:: Arco Research Group
"""
from __future__ import with_statement
import logging
from thread import allocate_lock
import threading
class Singleton(type):
"""A metaclass for make any other class a Singleton_ (the design pattern).
Example of use::
class MySingletonClass:
__metaclass__ = Singleton
# your code goes here :)
.. _Singleton: http://en.wikipedia.org/wiki/Singleton_pattern
"""
def __init__(cls, name, bases, dct):
cls.__lock = threading.Lock()
cls.__instance = None
type.__init__(cls, name, bases, dct)
def __call__(cls, *args, **kw):
with cls.__lock:
if cls.__instance is None:
cls.__instance = type.__call__(cls, *args, **kw)
return cls.__instance
def loaded(cls):
return cls.__instance != None
class Flyweight(type):
'''Flyweight dessign pattern (for identical objects)
class Sample(object):
__metaclass__ = Flyweight
def __init__(self, key, [...]):
[...]
'''
def __init__(cls, name, bases, dct):
cls.__instances = {}
type.__init__(cls, name, bases, dct)
def __call__(cls, key, *args, **kw):
instance = cls.__instances.get(key)
if instance is None:
instance = type.__call__(cls, key, *args, **kw)
cls.__instances[key] = instance
return instance
# Observer Pattern
class Observable:
'''Observer design pattern implementation.
Observable class:
* Constructor can optionally receive two params.
topics : A list of topic names (as strings)
logger : A logger from logging module
* Store a manage a dictionary with key:IdTopic, value:list of subscribers
'''
# Exceptions
class ObserverException(Exception):
def __str__(self):
return "%s: %s" % (self.__class__.__name__, Exception.__str__(self))
class TopicAlreadyExists(ObserverException): pass
class NotSuchTopic(ObserverException): pass
class InvalidTopicName(ObserverException): pass
class InvalidSubscriber(ObserverException): pass
class NotASubscriber(ObserverException): pass
def __init__(self, topics=['default'],
logger=logging.getLogger('Observable')):
self._logger = logger
self._logger.propagate = 0
self.__topics = {}
for topic in topics:
if not isinstance(topic, str):
raise self.InvalidTopicName()
self.__topics[topic] = []
def getTopicNames(self):
return self.__topics.keys()
def addTopic(self, topicName):
if topicName in self.__topics.keys():
raise self.TopicAlreadyExists()
if not isinstance(topicName, str):
raise self.InvalidTopicName()
self.__topics[topicName] = []
self._logger.info('New topic created for %s instance: %s' %
(str(self.__class__.__name__), topicName))
def removeTopic(self, topicName):
try:
del self.__topics[topicName]
except KeyError:
raise self.NotSuchTopic()
def attach(self, subscriber, topicName='default'):
if not callable(subscriber):
raise self.InvalidSubscriber()
try:
if subscriber in self.__topics[topicName]: return
self.__topics[topicName].append(subscriber)
except KeyError:
raise self.NotSuchTopic()
def detach(self, subscriber, topicName='default'):
try:
self.__topics[topicName].remove(subscriber)
except ValueError:
raise self.NotASubscriber()
except KeyError:
raise self.NotSuchTopic()
def _notify(self, sub, value):
sub(value)
def notify(self, topicName, value):
try:
for sub in self.__topics[topicName]:
try:
self._notify(sub, value)
except Exception, e:
self._logger.warning('The subscriber %s raises an exception' % sub)
self._logger.debug('Subscriber exception: %s' % e)
except KeyError:
raise self.NotSuchTopic()
def status(self):
'''Return the topic configurations compound by dictionary with
key:IdTopic and value:List of subscribers'''
return self.__topics.copy()
class ObjectObservable(Observable):
'''Observer design pattern implementation based in interfaces.
Observable class:
* Constructor can optionally receive two params.
topics : A dictionary k:id_topic v:callback_name (as string)
logger : A logger from logging module
* Store a manage a dictionary with key:IdTopic, value:list of subscribers'''
class InvalidObserverInterface(Observable.ObserverException): pass
class InvalidCallbackName(Observable.ObserverException): pass
def __init__(self, topics={'default':'update'},
logger=logging.getLogger('Observable')):
Observable.__init__(self, topics.keys(), logger)
#Topics:
# key: id_topic
# val:(str_callback, [subscribers_callbacks])
self.__interface = {}
for topicName, topicCb in topics.items():
if not isinstance(topicName, str):
raise self.InvalidTopic(topicName)
if not isinstance(topicCb, str):
raise self.InvalidObserverInterface(topicCb)
self.__interface[topicName] = topicCb
def addTopic(self, topic, callbackName):
'''Register a new topic. If the topic exists raise the
TopicAlreadyExists exception'''
if not isinstance(callbackName, str):
raise self.InvalidCallbackName()
if topic in self.__interface.keys():
raise Observable.TopicAlreadyExists(topic)
Observable.addTopic(self, topic)
self.__interface[topic] = callbackName
self._logger.debug('Added topic [%s] with callback [%s]' %
(str(topic), callbackName))
def removeTopic(self, topicName):
'''Unregister a topic. If the topic not exists raise the
NotSuchTopic exception'''
try:
del self.__interface[topic]
Observable.removeTopic(self, topicName)
self._logger.debug('Removed topic [%s]' % str(topic))
except KeyError:
raise self.NotSuchTopic()
def attach(self, subscriber, topicName='default'):
'''Subscribe a class into topic. If topic not is specified,
the subscriber is registered into default topic. If the topic
not exits raise NotSuchTopic exception'''
try:
meth = getattr(subscriber, self.__interface[topicName])
Observable.attach(self, meth, topicName)
self._logger.debug('Subscribed [%s]' % str(subscriber))
except KeyError:
raise self.NotSuchTopic(topicName)
except AttributeError:
raise self.InvalidObserverInterface()
def detach(self, subscriber, topic='default'):
'''Unsubscribe a subscriber class from a topic. If topic not
exist raise the NotSuchTopic exception. If the subscriber not
is subcribed into topic raise the NotSuchObserver exception'''
try:
meth = getattr(subscriber, self.__interface[topic])
Observable.detach(self, meth, topic)
self._logger.debug('Unsubscribe [%s] from [%s]' % \
(str(subscriber), str(topic)))
except AttributeError:
raise self.InvalidObserverInterface()
except KeyError:
raise Observable.NotSuchTopic()
class ObjectObservableAsync(ObjectObservable):
'''Observer design pattern implementation.
Observable Asynchronous class (one thread by notification).
* Constructor can optionally receive four params:
topics : A dictionary k:id_topic v:callback_name (as string)
pollSize: Size of thread poll for asyncronous notifications (15 by default)
logger : A logger from logging module
* Store a manage a dictionary with key:IdTopic, value:list of subscribers
* Store and manage the thread poll of asyncronous notifications
* Wait to end all the notifications
* If the thread poll is full the notifications will be ignore'''
class CallbackThread(threading.Thread):
def __init__(self, callback, value, onExit):
threading.Thread.__init__(self)
self._cb = callback
self._val = value
self._onExit = onExit
def run(self):
try:
self._cb(self._val)
finally:
self._onExit(self.getName())
def __init__(self, topics={'default':'update'},
pollSize=15, logger=logging.getLogger('Observable')):
ObjectObservable.__init__(self, topics, logger)
self._poll = pollSize
self._lockAT = allocate_lock()
self._activeThreads = 0
self._threads = {}
# Private Method
def _onExit(self, ident):
'''Unregister the thread of the active threads'''
self._lockAT.acquire()
self._activeThreads = self._activeThreads - 1
try:
del self._threads[ident]
except KeyError, e:
self._log.debug('Thread [%s] already removed' % ident)
finally:
self._lockAT.release()
# Private overwrite method
def _notify(self, subs_cb, value):
'''Overwrite the _nofify method to use asyncronous
notification. Start the method into Thread and register it'''
if self._poll >= self._activeThreads:
t = self.CallbackThread(subs_cb, value, self._onExit)
self._lockAT.acquire()
self._threads[t.getName()] = t
self._activeThreads = self._activeThreads + 1
self._lockAT.release()
t.start()
else:
self._log.error('Unable notify, full poll')
# Public overwrite method
def status(self):
'''Overwrite the status method to return the tuple status
compound by: Topics - Dictionary k:IdTopic, v:List of
subscribers Number Threads - Number of active threads
'''
return (self._topics.copy(), self._activeThreads)
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