Thinking Like a Programmer: Python Loops — Topic 2 — Lecture Summary

Topic 2: Loops — Thinking Like a Programmer (Python)
1. What Problem Do Loops Solve?

Don't start with syntax. Start with the problem.

 What if a task needs to happen 10 times?
 What if it needs to happen 10,000 times?
 How can we avoid repeating the same code?
 How do we decide when repetition should stop?

Key idea:

A loop allows a program to repeat instructions without writing the same instructions again.

2. Recognising Repetition in a Problem

Before writing code, ask: “What part of this problem is repeating?”

Example 1:

Display the numbers from 1 to 10.

Think:

1. Start at 1.
2. Display the number.
3. Move to the next number.
4. Stop after 10.

Then convert that thinking into Python.

3. for Loops — When You Know What to Iterate Over

Cover/ Example 2:

for number in range(1, 11):
print(number)

Then explain how to think about it, rather than just what each word means.

 What is changing?
 Where does it start?
 Where does it stop?
 How many times does the body execute?

, 4. Understanding range()

Break this into/ Example 3:

range(stop)
range(start, stop)
range(start, stop, step)

Include off-by-one errors, because these are important programming-thinking mistakes.

Example 4:

range(1, 10)

does not include 10.

Ask:

“If I need 1–10, what should my stopping value be?”



5. while Loops — When the Ending Point Depends on a Condition

Example 5:

number = 1

while number <= 10:
print(number)
number += 1

Focus on the programmer's reasoning:

Initial state → condition → action → state change → condition again

This is a much better way to understand while loops than memorising syntax.




6. Choosing the Correct Loop

Give yourself decision questions:

Do I have a sequence or known number of repetitions?