├── README.md
├── driver_observer1.py
├── driver_observer2.py
├── driver_observer3.py
├── observer1.py
├── observer2.py
└── observer3.py


/README.md:
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1 | Observer pattern in Python
2 | 


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/driver_observer1.py:
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 1 | from observer1 import Publisher, Subscriber
 2 | 
 3 | pub = Publisher()
 4 | 
 5 | bob = Subscriber('Bob')
 6 | alice = Subscriber('Alice')
 7 | john = Subscriber('John')
 8 | 
 9 | pub.register(bob)
10 | pub.register(alice)
11 | pub.register(john)
12 | 
13 | pub.dispatch("It's lunchtime!")
14 | 
15 | pub.unregister(john)
16 | 
17 | pub.dispatch("Time for dinner")
18 | 


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/driver_observer2.py:
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 1 | from observer2 import Publisher, SubscriberOne, SubscriberTwo
 2 | 
 3 | pub = Publisher()
 4 | bob = SubscriberOne('Bob')
 5 | alice = SubscriberTwo('Alice')
 6 | john = SubscriberOne('John')
 7 | 
 8 | pub.register(bob, bob.update)
 9 | pub.register(alice, alice.receive)
10 | pub.register(john)
11 | 
12 | pub.dispatch("It's lunchtime!")
13 | pub.unregister(john)
14 | pub.dispatch("Time for dinner")
15 | 


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/driver_observer3.py:
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 1 | from observer3 import Publisher, Subscriber
 2 | 
 3 | pub = Publisher(['lunch', 'dinner'])
 4 | bob = Subscriber('Bob')
 5 | alice = Subscriber('Alice')
 6 | john = Subscriber('John')
 7 | 
 8 | pub.register("lunch", bob)
 9 | pub.register("dinner", alice)
10 | pub.register("lunch", john)
11 | pub.register("dinner", john)
12 | 
13 | pub.dispatch("lunch", "It's lunchtime!")
14 | pub.dispatch("dinner", "Dinner is served")
15 | 


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/observer1.py:
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 1 | class Subscriber:
 2 |     def __init__(self, name):
 3 |         self.name = name
 4 |     def update(self, message):
 5 |         print('{} got message "{}"'.format(self.name, message))
 6 |         
 7 | class Publisher:
 8 |     def __init__(self):
 9 |         self.subscribers = set()
10 |     def register(self, who):
11 |         self.subscribers.add(who)
12 |     def unregister(self, who):
13 |         self.subscribers.discard(who)
14 |     def dispatch(self, message):
15 |         for subscriber in self.subscribers:
16 |             subscriber.update(message)
17 |         
18 | 


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/observer2.py:
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 1 | class SubscriberOne:
 2 |     def __init__(self, name):
 3 |         self.name = name
 4 |     def update(self, message):
 5 |         print('{} got message "{}"'.format(self.name, message))
 6 | class SubscriberTwo:
 7 |     def __init__(self, name):
 8 |         self.name = name
 9 |     def receive(self, message):
10 |         print('{} got message "{}"'.format(self.name, message))
11 |         
12 | class Publisher:
13 |     def __init__(self):
14 |         self.subscribers = dict()
15 |     def register(self, who, callback=None):
16 |         if callback == None:
17 |             callback = getattr(who, 'update')
18 |         self.subscribers[who] = callback
19 |     def unregister(self, who):
20 |         del self.subscribers[who]
21 |     def dispatch(self, message):
22 |         for subscriber, callback in self.subscribers.items():
23 |             callback(message)
24 |         
25 | 


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/observer3.py:
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 1 | class Subscriber:
 2 |     def __init__(self, name):
 3 |         self.name = name
 4 |     def update(self, message):
 5 |         print('{} got message "{}"'.format(self.name, message))
 6 |         
 7 | class Publisher:
 8 |     def __init__(self, events):
 9 |         # maps event names to subscribers
10 |         # str -> dict
11 |         self.events = { event : dict()
12 |                           for event in events }
13 |     def get_subscribers(self, event):
14 |         return self.events[event]
15 |     def register(self, event, who, callback=None):
16 |         if callback == None:
17 |             callback = getattr(who, 'update')
18 |         self.get_subscribers(event)[who] = callback
19 |     def unregister(self, event, who):
20 |         del self.get_subscribers(event)[who]
21 |     def dispatch(self, event, message):
22 |         for subscriber, callback in self.get_subscribers(event).items():
23 |             callback(message)
24 |         
25 | 


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