05 · REPEAT UNTIL A CONDITION CHANGES

Use while when you do not know the number of repeats

A for loop is a good fit when you have a collection and want to visit every item. A while loop is useful when you want to keep going until something changes. For example, let’s move a token around a simplified track until it reaches square 10.

position = 7

while position < 10:
    position = position + 1
    print("Now on square", position)

Python checks position < 10 before each pass. It prints 8, then 9, then 10. When the position is 10, the condition is false, so the loop stops.

Use for when you can say “once for each item.” Use while when you can say “keep doing this while the condition remains true.” Those two questions are usually enough to choose.

06 · FOLLOW THE VALUES

Trace a program instead of guessing

When code feels confusing, write down the values as Python runs each line. Here is a short example that totals a player’s cash after collecting two payments.

cash = 100
payments = [20, 15]

for payment in payments:
    cash = cash + payment

print(cash)

The output is 135. Notice that cash changes during each pass, while payment holds the current item from the list. A little table like this is a practical debugging tool: it shows exactly where your expectation and the program’s behavior begin to differ.

07 · A RISK-STYLE EXAMPLE

Check each territory against a simple rule

Here is a second setting from the course. In this simplified Risk-style exercise, each territory already tells us two things: who owns it, and whether it is next to the player's territory. We will look for neighboring territories owned by someone else. This is a practice rule for learning Python; it is not the full set of Risk rules.

territories = [
    {"name": "Northland", "owner": "Maya", "is_adjacent": True},
    {"name": "East Cape", "owner": "Luis", "is_adjacent": True},
    {"name": "South Ridge", "owner": "Luis", "is_adjacent": False},
]
player = "Maya"

for territory in territories:
    if territory["is_adjacent"] and territory["owner"] != player:
        print(territory["name"], "matches our practice rule")
    else:
        print(territory["name"], "does not match our practice rule")

The program prints that East Cape matches: it is adjacent, and Luis owns it rather than Maya. Northland is adjacent but Maya already owns it. South Ridge is owned by Luis, but it is not adjacent. Each territory must pass both checks to match the rule.

Notice how the loop and the condition have different jobs. The for loop says, “visit every territory.” The if says, “for this territory, check these two facts.” Keeping those jobs separate makes the code easier to explain and change.

08 · AN AIR-TRAFFIC-CONTROL EXAMPLE

Display a status without pretending to make the decision

Air traffic control is a serious, safety-critical setting, so our small Python example will have a very limited job: display a status that has already been entered by a controller or supplied by another trusted part of a system. This code does not decide whether an aircraft can move, and it is not suitable for real air-traffic operations.

Each flight in this example has a callsign and a clearance status. We will show one message for a cleared status, another for waiting, and a verification message for anything else. Handling the unexpected case matters: real data can be missing, mistyped, or use a value our program did not expect.

flights = [
    {"callsign": "NORTH 21", "status": "cleared"},
    {"callsign": "EAST 08", "status": "waiting"},
    {"callsign": "WEST 14", "status": "unknown"},
]

for flight in flights:
    if flight["status"] == "cleared":
        print(flight["callsign"], "— clearance received")
    elif flight["status"] == "waiting":
        print(flight["callsign"], "— waiting for an update")
    else:
        print(flight["callsign"], "— ask the controller to verify")

The for loop visits all three flights. The if and elif handle the two statuses we recognize. The final else catches the unfamiliar value "unknown" and asks for verification. It is safer and clearer to handle an unexpected value than to silently treat it as “cleared.”

This example shows a durable engineering habit: be clear about what your program is responsible for, and what it is not. In business systems, a display or report may show a decision made elsewhere; it should not quietly take over authority it was never designed or approved to have.

09 · CONNECTING TO ODOO

These same decisions appear in business software

Odoo methods often check a record’s values, choose a result, or process several records. The shape of the code will be familiar even when the business meaning is new.

for order in orders:
    if order.amount_total > 1000:
        print("Review this large order:", order.name)
    else:
        print("Normal order:", order.name)

This is plain Python illustrating the idea; it is not a complete Odoo method. orders stands for a group of orders, and each order has a total and a name. In later lessons, we will learn where Odoo records come from and how to write methods that follow Odoo’s conventions.

These examples also point to durable skills we will keep practicing: understand the business process before automating it, make each rule explicit, consider what the user is allowed to see or change, and test ordinary as well as unusual cases. AI can help write code, but it cannot safely guess what a business rule should mean. A person still needs to explain the process, check the design, and verify the result.

10 · TRY IT YOURSELF

Predict, run, and explain

1. Set position = 7 and roll = 5. What is new_position?
2. In the property example, change is_owned to True. Which message prints, and why?
3. In the Risk-style example, change East Cape's is_adjacent value to False. What message does it print now?
4. In the status-display example, change West 14's status to "waiting". Which branch handles it?
5. Add 25 to the payments list. What is the new total?
6. In the while example, change the starting position to 9. How many times does the loop run?
7. What could go wrong if a while loop never changes the value used by its condition?

Before running each example, say what you expect. Then run it and compare. If the output differs, trace the values line by line. That habit will serve you throughout Python and Odoo development.

11 · QUICK RECAP

What you can do now

• Use if, elif, and else to choose between actions.
• Use a for loop to handle each item in a collection.
• Use a while loop to repeat while a condition remains true.
• Trace changing values to understand what a program does.
• Explain the inputs and practice rule in a game example.
• Recognize these patterns in simple Odoo business logic.

Next, we will learn how to put related instructions into functions. That will let us give a name to a small piece of work and reuse it, such as “move the player” or “check whether an order needs review.”