10. Event Driven Programming Explained

Event Driven Programming Explained

The code below is my solution to the last TODO in the previous section. Below that you'll find a video walkthrough of the EventDrivenChatBot code.

Solution Overview

There are many ways to solve this problem, but most solutions probably involve modeling the "state" of the chatbot as either

  1. has NOT yet seen the message "age?" OR
  2. HAS seen the message "age?"

I implemented this by making three modifications…

  1. In __init__ I added a state variable has_been_asked_age which is initially set to False

  2. I define a function called handle_age_request which in turn calls either respond_to_age_request or respond_to_age_request_detailed depending on the STATE of the bot.

  3. Register a callback that associated handle_age_request to the "ask?" message. Note that I also removed two calls to register_callback that were there previously.

Start Quiz:

from datetime import datetime
import time

class EventDrivenChatBot:
    
    def __init__(self):
        self.accepted_messages = {}
        
        # 1. ADDED THIS "STATE" VARIABLE
        self.has_been_asked_age = False
        
        self.birth_time = datetime.now()
        
        # "registering" all callbacks
        self.register_callback("hi", 
                               self.respond_to_greeting)
        self.register_callback("bye", 
                               self.respond_to_departure)
        
        # 3. USING handle_age_request TO DISPATCH
        #    RESPONSES TO "age?"
        self.register_callback("age?",
                               self.handle_age_request)
    
    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!")
    
    # 2. ADD DISPATCH POINT FOR PROCESSING "age?" MESSAGE
    def handle_age_request(self):
        if not self.has_been_asked_age:
            self.has_been_asked_age = True
            self.respond_to_age_request()
        else:
            self.respond_to_age_request_detailed()
            
    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(1.3)
bot.handle_message("age?")
print("---No chatbot, let me ask you that again...")
bot.handle_message("age?")

08 V3

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