09. Event Driven Programming

Event Driven Programming - Chatbot

A chatbot is a perfect way to demonstrate event driven programming since we can't dictate in advance the "correct" sequence of statements a chatbot should make.

Instead, a chatbot should respond to "events" which come in the form of messages from the chatbot's conversation partner.

Goals for this activity

  1. (re)familiarize yourself with how Python handles classes and object oriented programming.

  2. gain familiarity with what types of problems event driven programming is good for.

  3. write simple code that works within this event driven framework

TODO 1 - Read through and understand the EventDrivenChatBot class

Read through the code below until you have a prediction for what will happen when you execute this code by pressing the Test Run button.

NOTE - the last few lines of the code below is where the EventDrivenChatBot class is instantiated and its methods are called.

Start Quiz: 

from datetime import datetime
import time

class EventDrivenChatBot:
    
    def __init__(self):
        # accepted_messages maps incoming messages to 
        # list of callback functions
        self.accepted_messages = {}
        
        # time of instantiation
        self.birth_time = datetime.now()
        
        # "registering" all callbacks
        self.register_callback("hi", 
                               self.respond_to_greeting)
        self.register_callback("bye", 
                               self.respond_to_departure)
        self.register_callback("age?",
                               self.respond_to_age_request)
        self.register_callback("age?",
                               self.respond_to_age_request_detailed)
    
    def register_callback(self, message, callback):
        """
        Registers a callback to a message.
        """
        if message not in self.accepted_messages:
            self.accepted_messages[message] = []
        self.accepted_messages[message].append(callback)
        
    def respond_to_greeting(self):
        print("Hello!")
        
    def respond_to_departure(self):
        print("Nice chatting with you!")
            
    def respond_to_age_request(self):
        age = datetime.now() - self.birth_time
        print("I am", age.seconds, "seconds old.")
        
    def respond_to_age_request_detailed(self):
        age = datetime.now() - self.birth_time
        micros = age.microseconds
        print("Technically, I'm", age.seconds, "seconds and", 
              micros, "microseconds old")
        
    def handle_message(self, message):
        if message not in self.accepted_messages:
            print("sorry, I don't understand", message)
        else:
            callbacks = self.accepted_messages[message]
            for callback in callbacks:
                callback() 
                
bot = EventDrivenChatBot()
bot.handle_message("hi")
time.sleep(2.2)
bot.handle_message("age?")
bot.handle_message("bye")

TODO 2 - Run the Code

Press the Test Run button above and look at the output. How does it compare to what you expected to see? What happens between calling the handle_message method and actually printing the chatbot's response?

TODO 3 - Modify the Code

Once you feel like you understand how this code works, modify EventDrivenChatBot so that the FIRST time it receives the message "age?" it calls respond_to_age_request but all subsequent "age?" messages should trigger a call to respond_to_age_request_detailed .

You can find my solution in the next section of this lesson.

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