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Stage 4: It Keeps Listening

Course progressStage 4 of 10
~35 min
Build

a command loop so the assistant keeps taking commands

Learn

how a while loop repeats and how break stops it

Ship

an assistant you can talk to over and over until you type quit

The big idea​

Right now your assistant answers exactly one command and then the program stops. A real assistant should keep listening — command after command — until you decide to stop. This is the most important stage in the whole course, because every skill you add later lives inside what you build today.

The tool is a loop — code that repeats. We'll use a while loop. while True: means "keep doing this forever." Everything indented under it runs again and again, from the top, each time around.

Forever sounds scary, so we need an exit. The break keyword breaks out of the loop immediately. We'll break when the user types quit. Every loop you ever write needs a clear way out — so we build the exit first.

New words
loop
Code that repeats. A while loop runs the same indented lines over and over.
while True
Repeat forever — until something inside the loop stops it.
break
Jump out of the loop right now and continue with the program after it.
Before you start

Make sure you finished Stage 3: It Reacts — your assistant should answer hello and bye.

Teacher demo

Show the room how to stop a running program: click the terminal and press Control + C. A while True loop runs until you break out of it or press Control + C. Campers should see that "stuck" is never scary — it's one keystroke away from stopped.

Build it​

Step 1 — Wrap the commands in a forever loop​

We take the command reading and the if/elif/else you already wrote and tuck them inside a while True: loop. The greeting stays outside — you only need to be greeted once, not every time around.

Trace it

Trace one trip around the loop

  1. while True: starts a round.
  2. command = input("> ") waits for you to type and press Return.
  3. The if/elif/else picks a reply and speaks it.
  4. The loop goes back to the top and asks for the next command.

Step 2 — Build the exit first​

Before any other command, give the loop a way out. If the user types quit, we say goodbye and break. Building the exit first means you can always stop your program — no runaway loops.

Think first

Why build quit first?

What would happen if your while True loop had no quit and no break?

Check your thinking

It would ask for commands forever with no way to stop except pressing Control + C. That's why we add the quit/break exit before anything else.

Python code task
Update your file

assistant.py

Where it goes: Replace your old command + if/elif/else block (from Stage 3) with this loop. Keep the import, speak function, and the name greeting above it.

Notice everything inside the loop is indented one level. The quit check comes first.

speak(f"Type commands, {name}. Type quit to stop.")

while True:
    command = input("> ")

    if command == "quit":
        speak("Goodbye for now!")
        break
    elif command == "hello":
        speak(f"Hello again, {name}!")
    elif command == "bye":
        speak("See you later!")
    else:
        speak("I don't know that one yet.")

Run it. Type hello, then bye, then hello again — it keeps answering. When you're done, type quit and it says goodbye and stops. Your assistant is finally waiting for you instead of running off.

Understand it​

That while True loop is the skeleton of your whole assistant. From now on, every new skill — jokes, the time, memory, the internet — is just another elif branch added inside this loop. You will never rebuild this structure; you'll only grow it. That's why we spent a whole stage on it.

We put the quit check at the very top of the loop on purpose. An exit that's easy to find is an exit that actually gets used — by you while testing, and by anyone who runs your program. A loop you can't stop isn't powerful, it's broken.

Try this​

Learning beat

Try this

Three short experiments. Predict before you run, then test your guess.

Predict first

What happens if you type quit with a capital Quit? Predict, then try. (Same capital-letter quirk as before — Stage 8 fixes it.)

Compare

Move the break line out from under the quit check so it runs every time. Run it. How many commands can you give before it stops? (Then put break back where it belongs.)

Connect

Your loop is getting a tall stack of elif branches. Imagine ten more skills in there. How might you keep each skill's code tidy and named? (Stage 5 packs each one into its own function.)

Test your stage​

Stuck? Compare carefully
Answer check
Debug compare only

assistant.py

Where it goes: Compare this against your whole file. Use it only if your program won't run.

This is the full file at the end of Stage 4.

import subprocess


def speak(text):
    print(text)
    subprocess.run(["say", text])


speak("Hi! My name is Pixel.")

name = input("What is your name? ")
speak(f"Nice to meet you, {name}!")
speak(f"Type commands, {name}. Type quit to stop.")

while True:
    command = input("> ")

    if command == "quit":
        speak("Goodbye for now!")
        break
    elif command == "hello":
        speak(f"Hello again, {name}!")
    elif command == "bye":
        speak("See you later!")
    else:
        speak("I don't know that one yet.")
  • You can type several commands in a row without the program ending.
  • Typing quit says goodbye and stops the program.
  • Typing an unknown command still gives a reply and keeps listening.
  • Design check. Is your quit check the first thing inside the loop? It should be the easiest exit to find.
  • From memory. Without looking, write the two lines that make quit stop the loop. Did you remember break?

If it breaks​

  • The program is "stuck" and won't stop. Click the terminal and press Control + C. That's the normal, safe way to stop any running program. If you have no quit/break, add one.
  • IndentationError. Everything inside the loop must be indented under while True:. The if/elif/else go one level deeper still.
  • It stops after one command. Your break is running every time, not just on quit. Make sure break is indented under the quit check.
  • It asks for a command but never speaks. Check that your if/elif/else lines are inside the loop, lined up under the command = input(...) line.