• Common pattern in programming is sending messages between senders and receivers.

    • The receivers are sometimes called listeners. ``` from datetime import datetime

      # This function returns the current time as a string
      def getCurrentTime(): return datetime.now().strftime(\%m-%d-%Y %H:%M:%S)

    # This contains two methods: a send method and a receive method. # Each function has a bunch of listeners within them and they are extended from the Messenger class class Messenger: def init(self, listeners=[]): self.listeners = listeners

      def send(self, message):
                   # Each listener is iterated through
      for listener in self.listeners:
                           # listener.receive is then called for the message. All of the listeners that are listening here will receive the message
          listener.receive(message)

  def receive(self, message):
      # Must be implemented by extending classes
      pass

    # This saves the messages and adds them to a list. It also saves the time that the messages was received class SaveMessages(Messenger): # Constructor is overwritten def init(self, listeners=[]): super().init(listeners) # This is the list where they are saved here: # We can add whatever custom attributes we want self.messages = []

      def receive(self, message):
                   # Every time a message is received, it adds it to the list of messages
      self.messages.append({'message': message, 'time': getCurrentTime()})
        
  def printMessages(self):
      for m in self.messages:
          print(f'Message: \{m[\message\]}\ Time: {m[\time\]}')
                   # The list of messages is reset here. It will only print out the message once and then clear it afterwards
      self.messages = []

listener = SaveMessages()

sender = Messenger([listener])

sender.send(‘Hello, there! This is the first message!’)

sender.send(‘This is the second message!’)

sender.send(‘This is the third message!’)

listener.printMessages()

* This will print out the following:

Messages: “Hello, there! This is the first message!” Time:10-09-2023 12:40:00 ```

  • It will do this for all three messages.
  • Tuples and Dictionaries can also be used to hold the messages. Another component is where do we put the list of messages.

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