Edexcel IAL Computer Science – U4.15 Pure, first-class and lambda functions – Lesson & Worksheet

Bespoke, fully editable lesson for Pearson Edexcel International A Level Computer Science (2026): U4.15 Pure, first-class and lambda functions. Slides, worksheet and full answers.

Written for Unit 4 Advanced Practical Programming, topic 20 Additional programming paradigms (specification 20.1.2 a, 20.1.2 b, 20.1.2 c, 20.1.2 d, 20.1.2 e, 20.1.2 f, 20.1.2 g, 20.1.2 h). Everything is editable, so you can adapt it to your class.

What’s included

• PowerPoint lesson (16 slides) with teacher notes on every slide
• Student worksheet (Word), ready to print or edit
• Answer sheet (Word) with mark-scheme style answers for every question

U4.15 Pure, first-class and lambda functions

By the end of the lesson students can:

• Write pure functions that avoid side effects and treat data as immutable
• Pass functions as arguments, return them from functions and write them as lambdas
• Use generators for lazy evaluation, and recursion in place of a loop

Worksheet sections: A. Key words; B. Predict the output; C. Amend to be pure; D. Exam-style questions; E. Challenge

Every lesson includes

• Learning goals and a starter question
• Clear explanations, diagrams and worked examples (Python 3 throughout, as the specification requires)
• A quick check and a “your turn” task linked to the worksheet
• Exam-style questions with marks, and an exit ticket

Format

• PowerPoint (.pptx) and Word (.docx), fully editable
• Works in PowerPoint and Google Slides
• Calm, muted sixth-form design, consistent across the whole course

These are independent resources written for the Pearson Edexcel International Advanced Level Computer Science specification (Issue 1, first teaching 2026; IAS XCP01, IAL YCP01). They are not produced or endorsed by Pearson.