Conditions, comparisons and if/elif/else. Learn through short examples, practical tasks and targeted questions.
Selection allows a program to take different paths depending on a condition. Python uses if, elif and else, with indentation showing which statements belong to each branch. Try values at either side of a threshold and exactly on the boundary.
Watch out: A single = assigns a value; == compares values. Confusing them causes errors in conditional expressions.
Conditions, comparisons and if/elif/else. Study the code and predict what it does before running it. Change a value or string and observe how the output changes.
temperature = 18
if temperature < 10:
print("Cold")
elif temperature < 20:
print("Mild")
else:
print("Warm")Create a ticket-price decision: under 12 costs £5, 12–17 costs £7, and adults cost £10.
Plan your inputs, processing and outputs. Write the code in Mu, IDLE or PyCharm; test at least three cases.
age = int(input("Age: "))
if age < 12:
print("£5")
elif age < 18:
print("£7")
else:
print("£10")Identify the problem and explain how to fix it before revealing the answer.
mark = 70
if mark >= 50
print("Pass")mark = 70
if mark >= 50:
print("Pass")Compare the two snippets. Identify the changed line, run the corrected version and explain the effect.
Extension: Improve your solution to deal with unexpected input, add a second feature or display results more clearly.
Reflect: What was the hardest part? What would you test if someone else used your program?
Want extra practice? Try interactive Python tracing and debugging questions →
Trace the condition first, deciding whether it is True or False before following either branch. Test values immediately below, equal to and above the boundary: those are the values most likely to expose mistakes.
Check: The if branch runs because >= includes equality.