Iteration using while loops
Lesson details
Learning outcome
I can use iteration to repeat sequences of code in a program and use a flag to stop a loop from running.
Key learning points
- Condition controlled iteration will execute until a condition is met.
- While loops are used for condition controlled iteration in Python.
- Flags can be used to start and stop a loop in a program.
Keywords
Iteration - the process of repeating a sequence of instructions within a program loop
Condition - an expression that evaluates to True or False
Flag - a signal that is used to let a program know whether a condition has been met or not
Common misconception
A while loop is the most appropriate loop to use when you know exactly how many iterations will need to be performed.
While loops should be used when the number of iterations can change. Even though while loops can be used in this way, for loops are a more appropriate choice as they will track the number of iterations as part of their operation.
Teacher tip
The number of times a program iterates through a sequence of code can sometimes be confusing for pupils. Encourage them to test programs and reflect on how many times the loop is executed. They could use debugging tools or by outputting a counting variable.
Equipment
Pupils will need access to a device that can edit and run Python programs. Examples in this lesson use the RPF Code Editor https://oak.link/python-editor
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.You can use multiple elif blocks.
Q2.A program calculates a theme park ticket price by first checking the users age and then checking if it is peak season or not. Which of the following is used in the program?
Q3.Match the relational operator to it's description.
greater than
less than
not equal to
equal to
less than or equal to
more than or equal to
Q4.What will be the output of the following Python code?
12345678score = 50
if score >= 80:
print("Win")
elif grade >= 50:
print("Try again")
else:
print("You lose")Code colour
Q5.Which of the following statements about nested if statements is true?
Q6.A school organises students based on age. Students 11-16 attend High School, and students 16-18 Sixth Form. Which expression correctly checks if a student's age falls within the High School range?
Assessment exit quiz
5 Questions
Q1.What does 'iteration' mean in programming?
Q2.What is the purpose of a flag in programming?
Q3.What while loop should you use if you want a block of code to run forever?
Q4.In Python, which of the following is a way to create a flag variable named is_game_over and set its initial value to False?
Q5.What is treasure_found in this code?
12345distance_traveled = 0
treasure_found = False
while treasure_found == False:
print(f"Keep going {distance_traveled} steps travelled so far")Code colour
To help you plan your 8 computing lesson on: Iteration using while loops, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 8 computing lesson on: Iteration using while loops, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 3 computing lessons from the Introduction to Python programming unit, dive into the full secondary computing curriculum, or learn more about lesson planning.