UK K12 GCSE A-Level Year 7 KS3 Computer Science Python Conditionals and Loops

Learning Objectives

By the end of this topic, students will be able to:

• Explain the purpose and syntax of conditional statements in Python, including if, elif, and else.
• Write and execute Python code that uses conditional statements to make decisions.
• Describe the use of loops in Python, including for and while loops.
• Write and execute Python code that uses loops to repeat tasks.
• Identify and correct common errors in conditional and loop statements.

Core Concepts

Conditional statements in Python allow the program to make decisions based on certain conditions. The if statement is used to check if a condition is true, and if it is, the code inside the if block is executed. The elif statement is used to check another condition if the first one is false, and the else statement is used to execute code if all conditions are false.

Loops in Python allow the program to repeat a task multiple times. The for loop is used to iterate over a sequence (such as a list or string), and the while loop is used to repeat a task while a certain condition is true.

Conditional Statements

• if statement: if condition: code
• elif statement: elif condition: code
• else statement: else: code

Loops

• for loop: for variable in sequence: code
• while loop: while condition: code

Example of Conditional Statement

x = 5
if x > 10:
    print("x is greater than 10")
elif x == 5:
    print("x is equal to 5")
else:
    print("x is less than 10")

Example of Loop

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

Worked Examples

Example 1: Conditional Statement

Write a Python program that asks the user for their age and prints out a message based on their age.

age = int(input("Enter your age: "))
if age >= 18:
    print("You are an adult.")
elif age >= 13:
    print("You are a teenager.")
else:
    print("You are a child.")

Example 2: Loop

Write a Python program that prints out the numbers from 1 to 10.

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

Common Misconceptions

• Misconception 1: Thinking that the if statement only checks if a condition is true, without considering the elif and else statements.
• Misconception 2: Thinking that the for loop only iterates over a list, without considering other sequences such as strings and tuples.
• Misconception 3: Thinking that the while loop only repeats a task while a condition is true, without considering the use of break and continue statements.

Exam Tips

• Make sure to read the question carefully and understand what is being asked.
• Use the if, elif, and else statements to make decisions based on conditions.
• Use the for and while loops to repeat tasks.
• Identify and correct common errors in conditional and loop statements.
• Practice writing Python code that uses conditional and loop statements.

MCQs

MCQ 1: [F]

What is the purpose of the if statement in Python?

A) To repeat a task multiple times B) To make a decision based on a condition C) To iterate over a sequence D) To print a message to the user

Correct answer: B) To make a decision based on a condition

Why the distractors fail: A) The if statement is not used to repeat a task, but rather to make a decision.
C) The for loop is used to iterate over a sequence, not the if statement.
D) The print statement is used to print a message to the user, not the if statement.

MCQ 2: [H]

What is the syntax of a for loop in Python?

A) for variable in sequence: code B) while condition: code C) if condition: code D) else: code

Correct answer: A) for variable in sequence: code

Why the distractors fail: B) The while loop is used to repeat a task while a condition is true, not the for loop.
C) The if statement is used to make a decision based on a condition, not the for loop.
D) The else statement is used to execute code if all conditions are false, not the for loop.

MCQ 3: [F]

What is the purpose of the else statement in Python?

A) To make a decision based on a condition B) To repeat a task multiple times C) To iterate over a sequence D) To execute code if all conditions are false

Correct answer: D) To execute code if all conditions are false

Why the distractors fail: A) The if statement is used to make a decision based on a condition, not the else statement.
B) The while loop is used to repeat a task while a condition is true, not the else statement.
C) The for loop is used to iterate over a sequence, not the else statement.

MCQ 4: [H]

What is the syntax of a while loop in Python?

A) while condition: code B) for variable in sequence: code C) if condition: code D) else: code

Correct answer: A) while condition: code

Why the distractors fail: B) The for loop is used to iterate over a sequence, not the while loop.
C) The if statement is used to make a decision based on a condition, not the while loop.
D) The else statement is used to execute code if all conditions are false, not the while loop.

MCQ 5: [F]

What is the purpose of the break statement in Python?

A) To repeat a task multiple times B) To make a decision based on a condition C) To iterate over a sequence D) To exit a loop prematurely

Correct answer: D) To exit a loop prematurely

Why the distractors fail: A) The while loop is used to repeat a task while a condition is true, not the break statement.
B) The if statement is used to make a decision based on a condition, not the break statement.
C) The for loop is used to iterate over a sequence, not the break statement.

Short-answer questions

Question 1

Write a Python program that asks the user for their age and prints out a message based on their age.

Question 2

Write a Python program that prints out the numbers from 1 to 10.

Question 3

Explain the purpose of the if, elif, and else statements in Python.

Question 4

Explain the purpose of the for and while loops in Python.

Question 5

What is the syntax of a for loop in Python?