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# Copyright (c) 2008 David Aguilar
"""This module provides the Observable class"""
from __future__ import division, absolute_import, unicode_literals
class Observable(object):
"""Handles subject/observer notifications."""
def __init__(self):
self.notification_enabled = True
self.observers = {}
def add_observer(self, message, observer):
"""Add an observer for a specific message."""
observers = self.observers.setdefault(message, set())
observers.add(observer)
def remove_observer(self, observer):
"""Remove an observer."""
for message, observers in self.observers.items():
if observer in observers:
observers.remove(observer)
def notify_observers(self, message, *args, **opts):
"""Pythonic signals and slots."""
if not self.notification_enabled:
return
# observers can remove themselves during their callback so grab a copy
observers = set(self.observers.get(message, set()))
for method in observers:
method(*args, **opts)
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