Python Examples

Python/Behavioral/ChainOfResponsibility.py

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+import inspect
+
+class Account:
+ _successor = None
+ _balance = None
+
+ def setNext(self, account):
+ self._successor = account
+
+ def pay(self, amountToPay):
+ import inspect
+ myCaller = inspect.stack()[1][3]
+ if self.canPay(amountToPay):
+ print "Paid " + str(amountToPay) + " using " + myCaller
+ elif (self._successor):
+ print "Cannot pay using " + myCaller + ". Proceeding .."
+ self._successor.pay(amountToPay)
+ else:
+ raise ValueError('None of the accounts have enough balance')
+ def canPay(self, amount):
+ return self.balance >= amount
+
+class Bank(Account):
+ _balance = None
+
+ def __init__(self, balance):
+ self.balance = balance
+
+class Paypal(Account):
+ _balance = None
+
+ def __init__(self, balance):
+ self.balance = balance
+
+class Bitcoin(Account):
+ _balance = None
+
+ def __init__(self, balance):
+ self.balance = balance
+
+if __name__ == '__main__':
+ bank = Bank(100)
+ paypal = Paypal(200)
+ bitcoin = Bitcoin(300)
+
+ bank.setNext(paypal)
+ paypal.setNext(bitcoin)
+
+ bank.pay(259)

Python/Behavioral/Command.py

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+class Bulb:
+ def turnOn(self):
+ print "Bulb has been lit"
+
+ def turnOff(self):
+ print "Darkness!"
+
+class Command:
+ def execute(self):
+ pass
+
+ def undo(self):
+ pass
+
+ def redo(self):
+ pass
+
+class TurnOn(Command):
+ _bulb = None
+
+ def __init__(self, bulb):
+ self._bulb = bulb
+
+ def execute(self):
+ self._bulb.turnOn()
+
+ def undo(self):
+ self._bulb.turnOff()
+
+ def redo(self):
+ self.execute()
+
+class TurnOff(Command):
+ _bulb = None
+
+ def __init__(self, bulb):
+ self.bulb = bulb
+
+ def execute(self):
+ self.bulb.turnOff()
+
+ def undo(self):
+ self.bulb.turnOn()
+
+ def redo(self):
+ self.execute()
+
+class RemoteControl:
+ def submit(self, command):
+ command.execute()
+
+if __name__ == '__main__':
+ bulb = Bulb()
+
+ turnOn = TurnOn(bulb)
+ turnOff = TurnOff(bulb)
+
+ remote = RemoteControl()
+ remote.submit(turnOn) # Bulb has been lit!
+ remote.submit(turnOff) # Darkness!

Python/Behavioral/Iterator.py

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+class RadioStation:
+ _frequency = None
+
+ def __init__(self, frequency):
+ self._frequency = frequency
+
+ def getFrequency(self):
+ return self._frequency
+
+class StationList:
+ _stations = []
+ _counter = 0
+
+ def addStation(self, station):
+ self._stations.append(station)
+
+ def removeStation(self, toRemove):
+ toRemoveFrequency = toRemove.getFrequency()
+ self._stations = filter(lambda station: station.getFrequency() != toRemoveFrequency, self._stations)
+
+ def __iter__(self):
+ return iter(self._stations)
+
+ def next(self):
+ self._counter += 1
+
+if __name__ == '__main__':
+ stationList = StationList()
+
+ stationList.addStation(RadioStation(89))
+ stationList.addStation(RadioStation(101))
+ stationList.addStation(RadioStation(102))
+ stationList.addStation(RadioStation(103))
+
+ for station in stationList:
+ print station.getFrequency()
+
+ stationList.removeStation(RadioStation(89))
+
+ for station in stationList:
+ print station.getFrequency()

Python/Behavioral/Mediator.py

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+class ChatRoomMediator:
+ def showMessage(self, user, message):
+ pass
+
+class ChatRoom(ChatRoomMediator):
+ def showMessage(self, user, message):
+ import datetime
+ time = datetime.datetime.now()
+ sender = user.getName()
+
+ print str(time) + '[' + sender + ']: ' + message
+
+class User:
+ _name = None
+ _chatMediator = None
+
+ def __init__(self, name, chatMediator):
+ self.name = name
+ self._chatMediator = chatMediator
+
+ def getName(self):
+ return self.name
+
+ def send(self, message):
+ self._chatMediator.showMessage(self, message)
+
+if __name__ == '__main__':
+ mediator = ChatRoom()
+
+ john = User('John Doe', mediator)
+ jane = User('Jane Doe', mediator)
+
+ john.send('Hi There!')
+ jane.send('Hey!')

Python/Behavioral/Memento.py

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+class EditorMemento:
+ _content = None
+
+ def __init__(self, content):
+ self.content = content
+
+ def getContent(self):
+ return self.content
+
+class Editor:
+ _content = ''
+
+ def type(self, words):
+ self._content = self._content + ' ' + words
+
+ def getContent(self):
+ return self._content
+
+ def save(self):
+ return EditorMemento(self._content)
+
+ def restore(self, memento):
+ self.content = memento.getContent()
+
+editor = Editor()
+editor.type('This is the first sentence')
+editor.type('This is the second.')
+
+#Save the state to restore to : This is the first sentence. This is second.
+saved = editor.save()
+editor.type('And this is the third')
+
+print editor.getContent() # This is the first sentence. This is second. And this is third.
+
+editor.restore(saved)
+editor.getContent() # This is the first sentence. This is second.

Python/Behavioral/Observer.py

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+class JobPost:
+ _title = None
+
+ def __init__(self, title):
+ self.title = title
+
+ def getTitle(self):
+ return self.title
+
+class JobSeeker:
+ _name = None
+
+ def __init__(self, name):
+ self.name = name
+
+ def onJobPosted(self, job):
+ print 'Hi ' + self.name + '! New job posted: ' + job.getTitle()
+
+class EmploymentAgency:
+ _observers = []
+
+ def notify(self, jobPosting):
+ for observer in self._observers:
+ observer.onJobPosted(jobPosting)
+
+ def attach(self, observer):
+ self._observers.append(observer)
+
+ def addJob(self, jobPosting):
+ self.notify(jobPosting)
+
+
+johnDoe = JobSeeker('John Doe')
+janeDoe = JobSeeker('Jane Doe')
+
+jobPostings = EmploymentAgency()
+jobPostings.attach(janeDoe)
+jobPostings.attach(johnDoe)
+
+jobPostings.addJob(JobPost('Software Engineer'))
+'''
+Output
+Hi John Doe! New job posted: Software Engineer
+Hi Jane Doe! New job posted: Software Engineer
+'''

Python/Behavioral/State.py

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+class WritingState:
+ def write(self, words):
+ pass
+
+class UpperCase(WritingState):
+ def write(self, words):
+ print words.upper()
+
+class LowerCase(WritingState):
+ def write(self, words):
+ print words.lower()
+
+class DefaultText(WritingState):
+ def write(self, words):
+ print words
+
+class TextEditor():
+ _state = None
+
+ def __init__(self, state):
+ self._state = state
+
+ def setState(self, state):
+ self._state = state
+
+ def type(self, words):
+ self._state.write(words)
+
+editor = TextEditor(DefaultText())
+editor.type('First Line')
+editor.setState(UpperCase())
+
+editor.type('Second Line')
+editor.type('Third Line')
+
+editor.setState(LowerCase())
+
+editor.type('Fourth Line')
+editor.type('Fifth Line')

Python/Behavioral/Strategy.py

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+class SortStrategy:
+ def sort(self, dataset):
+ pass
+
+class BubbleSortStrategy(SortStrategy):
+ def sort(self, dataset):
+ print 'Sorting using bubble sort'
+
+ return dataset
+
+class QuickSortStrategy(SortStrategy):
+ def sort(self, dataset):
+ print 'Sorting using quick sort'
+ return dataset
+
+class Sorter:
+ _sorter = None
+
+ def __init__(self, sorter):
+ self._sorter = sorter
+
+ def sort(self, dataset):
+ return self._sorter.sort(dataset)
+
+dataset = [1, 5, 4, 3, 2, 8]
+
+sorter = Sorter(BubbleSortStrategy())
+sorter.sort(dataset)
+
+sorter = Sorter(QuickSortStrategy())
+sorter.sort(dataset)