This PCEP practice question tests your understanding of functions, tuples, dictionaries and exceptions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer is using a lambda function that takes two arguments and returns their sum. Which of the following lambda expressions is correct?
lambda a, b: a + b
Correct lambda syntax with implicit return.
lambda a, b: a + b
Why wrong: Option D is same as B but incorrectly labeled; actually B is correct.
lambda a, b: return a + b
Why wrong: Lambda cannot contain a return statement; it implicitly returns the expression.
def add(a, b): return a + b
Why wrong: This is a function definition, not a lambda.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
lambda a, b: a + b
Option A is correct because a lambda function in Python is defined using the `lambda` keyword, followed by a comma-separated list of parameters, a colon, and a single expression that is implicitly returned. The expression `a + b` computes the sum of the two arguments without needing an explicit `return` statement, making it the proper syntax for a lambda that returns the sum.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
lambda a, b: a + b
Why this is correct
Correct lambda syntax with implicit return.
Related concept
Read the scenario before looking for a memorised answer.
lambda a, b: a + b
Why it's wrong here
Option D is same as B but incorrectly labeled; actually B is correct.
lambda a, b: return a + b
Why it's wrong here
Lambda cannot contain a return statement; it implicitly returns the expression.
def add(a, b): return a + b
Why it's wrong here
This is a function definition, not a lambda.
Common exam traps
Python Institute often tests the misconception that lambda requires an explicit `return` statement, leading candidates to choose Option C, but in reality the expression after the colon is automatically returned.
Detailed technical explanation
Lambda functions in Python are syntactic sugar for creating small anonymous functions; they are limited to a single expression that is evaluated and returned automatically. Under the hood, a lambda like `lambda a, b: a + b` creates a function object that is equivalent to `def add(a, b): return a + b`, but the lambda cannot contain statements, assignments, or multiple expressions. This makes lambdas ideal for short, throwaway operations such as sorting with a custom key or mapping over iterables, where defining a full function would be unnecessarily verbose.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the PCEP exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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FAQ
Functions, Tuples, Dictionaries and Exceptions — This question tests Functions, Tuples, Dictionaries and Exceptions — Read the scenario before looking for a memorised answer..
The correct answer is: lambda a, b: a + b — Option A is correct because a lambda function in Python is defined using the `lambda` keyword, followed by a comma-separated list of parameters, a colon, and a single expression that is implicitly returned. The expression `a + b` computes the sum of the two arguments without needing an explicit `return` statement, making it the proper syntax for a lambda that returns the sum.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This PCEP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCEP exam.
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