DSE ICT | Python Basics: a ten-section tutor guide (variables, loops, functions, debugging)

2026-11-05

Students follow an example but freeze at a blank file because they treat a program as syntax to memorise rather than a sequence of instructions. This lesson does one thing: take the sum from 1 to 10 and add variables, a loop and a function in turn, so the same task grows from three lines to ten and every change can be explained.

Objectives — Students can: (1) use a variable to hold and update a running total, stating its value after each line; (2) use a for loop with range for repeated arithmetic, setting the start and stop correctly; (3) wrap the logic in a function, pass an argument and return a result, then verify it with a test value.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Input and output	What do print and input do?	Print shows text, input collects a string
Data types	Why convert what input returns?	Input gives a string, so int is needed
Indentation	How does Python group instructions?	By indentation, usually four spaces

02 Lesson flow (45 minutes)

Time	Stage	Tutor does	Student does
0-6 min	Read a broken program	Project a five-line sum that fails and ask students to find the faults	Students name at least one fault
6-14 min	A variable is a box	Trace total equals total plus i turn by turn on the board	Students hand-write three rounds
14-24 min	for and range	Explain why range of 1 to 11 stops at 10: start included, stop excluded	Students rewrite for 1 to 100 and check 5050
24-32 min	Wrap it in a function	Define total_to with a parameter and return; contrast return with print	Students wrap the sum and call it once
32-40 min	Test and debug	Test with 1, 10 and 100, one of which fails deliberately	Students find and fix the failure
40-45 min	Exit check	Collect three answers, read only	Work alone

03 Teaching script (read it out)

Scene 1: Open with a broken program

Do not start with syntax. Project a five-line sum holding three faults: total never initialised, range written as 1 to 10, and one line indented to two spaces. Pairs hunt for faults, then their findings go back on the board.
The purpose is to show that programming is mostly fault finding, not writing from scratch. Once that is established, a blank file stops being frightening.

Students do: find the three faults and say what each one breaks.

Scene 2: Variables: boxes updated in turn

Draw one box labelled total and update it round by round: after round one it holds 1, after round two it holds 3, after round three it holds 6. Ask students for round ten, which is 55.
The common misreading is that total equals total plus i is an equation. Say clearly that the right side is evaluated first and the result is put back into the box. That wording lands better than the phrase assignment operator.

Students do: fill a ten-row table of i and total.

Scene 3: for and range: the stop is excluded

The range from 1 to 11 produces ten numbers, and writing 1 to 10 instead loses the 10, which is where marks disappear. One line printing the list makes it visible in a second, better than any explanation.
Then change the task from 1 to 10 into 1 to 100, whose answer is 5050, and let students press it themselves. Same task, different number: students see that the procedure matters, not the arithmetic.

Students do: rewrite for 1 to 100 and explain why 101 appears.

Scene 4: Wrap it in a function

Define total_to taking n, loop over 1 to n plus 1, and return the total. Two points must be explicit: n plus 1 exists because the stop is excluded, and return hands a value back rather than printing it.
Show print of total_to ten against assigning it to x: only the second can be used again. Once that is clear, students stop writing functions that are one long print statement.

Students do: rewrite the function for any n and verify n equals 10 gives 55.

Scene 5: Debug by breaking it on purpose

Give three test values, 1, 10 and 100, expecting 1, 55 and 5050. Then change the loop to stop at n, rerun with 10, and the result is 45, exactly 10 short. Ask students to find the gap and explain it.
That deliberate failure shows why testing matters: a program tested only with 1 passes even when broken. This is usually the quietest, most focused ten minutes of the lesson.

Students do: find the gap between 45 and 55 and write its cause in one line.

04 Question types and worked steps

Type	Example	Steps	Answer
Fill the blank	One line missing from a program	Trace the data flow before the syntax	Indentation and names both correct
Trace	Given a program and input, state the output	Write every variable value, one row per line	Include lines where nothing changes
Debug	One logical fault in the code	Test a small input first, then locate it	Name the line and the reason
Write	Produce a function from a description	Define input, processing and output	Has a return and a test value

Sanity check (teach this): Sanity checks: (1) the sums 55 and 5050 are landmarks worth memorising; (2) a result of 45 means one value was skipped, usually a wrong stop in range; (3) endless output means the loop variable is never updated; (4) a TypeError usually means input was not converted with int; (5) no function is finished until it has passed two different inputs.

05 Independent practice (3 questions)

Question	Answer	What to watch
Trace	Write the total after each round for 1 to 10	Check rounds one, two and ten
Debug	Fix the 1 to 10 range and explain	Check the explanation mentions the excluded stop
Write	Write total_to for any n and test 100	Check it returns 5050

06 Common mistakes and what to say

Mistake	Student writes	Say this
Total never initialised	Writing total equals total plus i straight away	“Total does not exist in round one. Give it a zero first.”
Wrong stop in range	Writing 1 to 10 and losing the final value	“Your answer is 10 short. The stop is excluded, so write 11.”
Print instead of return	A function that only prints, so nothing comes back	“Print shows, return hands over. Which one does the caller need?”
Inconsistent indentation	One line at four spaces and the next at two	“These look alike but Python reads them as different blocks. Line them up.”

07 Homework (paper, section and question numbers)

Redo this chapter — All three practice items with test values
ICT index — Other chapters and question types
All prep guides — The same ten sections across subjects

08 Exit check (last 5 minutes)

Question	Answer	Decision
Updating a variable	Right side first, then the box	Cannot state it, redo act two
range boundaries	Start included, stop excluded	Boundary wrong, redo act three
return versus print	Return hands back, print shows	Confused, redo act four

09 Tutor FAQ

Must students memorise syntax?

No. Recognise four shapes: assignment, for, def and return.

Which Python version?

Python 3 style; the exam does not demand a version, but input must be converted.

What if they cannot start?

Write three steps in plain words first: input, processing, output, then translate line by line.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.