AI App Development · Session 3: Building a Chat Loop

Step 1: The chat loop

A chatbot is a loop. It reads a message, decides on a reply, prints it, and repeats.

Python

def get_reply(message):
    return "You said: " + message

while True:
    message = input("You: ")
    if message == "quit":
        print("Bot: Goodbye!")
        break
    print("Bot:", get_reply(message))

Output

You: hello
Bot: You said: hello
You: nice day
Bot: You said: nice day
You: quit
Bot: Goodbye!

Notice we put the decision-making in its own function, get_reply. The loop doesn’t care how the reply is made. That will matter in a moment.

Step 2: Deciding how to reply

A rule-based bot looks for keywords and picks a reply with if statements.

Python

def get_reply(message):
    text = message.lower()
    if "hello" in text or "hi" in text.split():
        return "Hello! How can I help you study?"
    if "help" in text:
        return "Try typing 'quiz' and I'll ask you a question."
    if "thanks" in text:
        return "You're welcome!"
    return "I'm not sure about that. Type 'help' to see what I can do."

print(get_reply("Hello there"))
print(get_reply("can you HELP me"))
print(get_reply("what is a volcano"))

Output

Hello! How can I help you study?
Try typing 'quiz' and I'll ask you a question.
I'm not sure about that. Type 'help' to see what I can do.

.lower() turns the message into lowercase so capital letters don’t matter. The last line is a fallback: what the bot says when it doesn’t understand. Good bots always have a polite fallback.

Step 3: Remembering the conversation

A chat is more than one message. A real AI model uses what was said earlier to answer follow-up questions. We store the conversation in a list, called a history.

Python

history = []

history.append({"who": "user", "text": "Hi!"})
history.append({"who": "bot", "text": "Hello!"})
history.append({"who": "user", "text": "Tell me a fact."})

print(len(history), "messages so far")
for turn in history:
    print(turn["who"] + ":", turn["text"])

Output

3 messages so far
user: Hi!
bot: Hello!
user: Tell me a fact.

In your chat loop, append each user message and each bot reply to the history. Then pass the history to the reply function so it can use it later:

Python

def get_reply(message, history):
    if len(history) == 0:
        return "Nice to meet you!"
    return "We've been chatting for " + str(len(history)) + " messages."

Step 4: A quiz mode

Chatbots can have modes. Here is a small quiz mode that keeps score.

Python

questions = [
    {"q": "What is 7 x 8?", "a": "56"},
    {"q": "What is the capital city of Tanzania?", "a": "dodoma"},
]

score = 0
for item in questions:
    answer = input(item["q"] + " ")
    if answer.strip().lower() == item["a"]:
        print("Correct!")
        score += 1
    else:
        print("Not quite. The answer is", item["a"])

print("Score:", score, "out of", len(questions))

Output

What is 7 x 8? 56
Correct!
What is the capital city of Tanzania? dar es salaam
Not quite. The answer is dodoma
Score: 1 out of 2

.strip() removes extra spaces and .lower() ignores capitals, so ” Dodoma ” counts as correct.

Step 5: Why this matters

Your bot works with if statements. A real AI model replaces the if statements: instead of keywords, a model reads the whole message and writes a reply.

But your app around it stays almost the same: a loop, a history, a function that returns a reply. Next session we’ll connect get_reply() to a real model, safely.

Programs

Projects

Global Initiatives

Building a Chat Loop

Goals

Words to know

The lesson

Step 1: The chat loop

Step 2: Deciding how to reply

Step 3: Remembering the conversation

Step 4: A quiz mode

Step 5: Why this matters

Teach the bot three new tricks

Study buddy bot

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