SS 3 First Term

Lesson objectives

By the week's close, candidates should be able to:

1. Define function, parameter and return.
2. Write a function that averages a list.
3. Apply append, index and len.
4. Store a record in a dictionary.
5. Trace two calls.

Key vocabulary

• Function: a named block performing one task.
• Parameter: a variable named in a definition.
• Return value: the result sent to the caller.
• List: an ordered collection read by index.
• Dictionary: a set of key and value pairs.

Common misconceptions

• "A parameter and an argument are the same." The parameter is the name; the argument is the supplied value.
• "Index 1 is always the first item." Python counts from 0.

Teacher activities

1. Starter: trace a two-call function.
2. Teach definition, call and return.
3. Model average(marks) with a guard.
4. Extend to append and lookup.
5. Set two test lists.
6. Review index errors.

Student activities

1. Complete the starter trace.
2. Label parameters and arguments.
3. Type average(marks) and call it twice.
4. Append 90 and recalculate.
5. Build a three-key dictionary.
6. Repair an IndexError.

def average(marks):
    if len(marks) == 0:
        return 0
    return sum(marks) / len(marks)

scores = [62, 48, 71, 55]
print("Average:", average(scores))
scores.append(90)
print("Rounded:", round(average(scores), 1))
student = {"name": "Amaka", "score": 71}
print(student["name"], student["score"])

Expected output:

Average: 59.0
Rounded: 65.2
Amaka 71

Practical / learning evidence

ss3_scores_okoro.py defines average(marks), calls it on two lists, prints one rounded result and reads one dictionary record. Success needs an empty-list guard and two returned values.

Resources and preparation

Python 3, projector and a prepared empty list. Offline route: hand trace both calls beside the printed code.

Assessment for learning

Inspect the guard, the division and both calls. Award marks for argument order and dictionary access.

Inclusion and homework

Supply the function header; extend others to a highest(marks) function. Homework: write lowest(a, b, c) with one test call.