This PCEP practice question tests your understanding of control flow, loops, lists and logic. 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 company needs to filter a list of temperatures in Celsius to only those above 0, then convert to Fahrenheit (multiply by 9/5 and add 32). Which code snippet correctly accomplishes this using a list comprehension?
[t*9/5+32 for t in temps if t>0]
Correct list comprehension with expression and filter.
[t for t in temps if t>0 then t*9/5+32]
Why wrong: Invalid syntax: 'then' is not a keyword in list comprehensions.
[t*9/5+32 for t in temps if t>0 else 0]
Why wrong: Invalid syntax: else not allowed in list comprehension filter.
[t*9/5+32 for t in temps if t>0 else t]
Why wrong: Invalid syntax: else not allowed in list comprehension filter.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
[t*9/5+32 for t in temps if t>0]
Option A is correct because it uses the standard list comprehension syntax: `[expression for item in iterable if condition]`. Here, `t*9/5+32` is the expression that converts Celsius to Fahrenheit, `for t in temps` iterates over the list, and `if t>0` filters out temperatures at or below zero. This produces a new list containing only the Fahrenheit equivalents of positive Celsius temperatures.
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.
[t*9/5+32 for t in temps if t>0]
Why this is correct
Correct list comprehension with expression and filter.
Related concept
Read the scenario before looking for a memorised answer.
[t for t in temps if t>0 then t*9/5+32]
Why it's wrong here
Invalid syntax: 'then' is not a keyword in list comprehensions.
[t*9/5+32 for t in temps if t>0 else 0]
Why it's wrong here
Invalid syntax: else not allowed in list comprehension filter.
[t*9/5+32 for t in temps if t>0 else t]
Why it's wrong here
Invalid syntax: else not allowed in list comprehension filter.
Common exam traps
Python Institute often tests the distinction between the filter `if` (placed after the `for` clause) and the conditional expression `if-else` (placed in the expression part), and the trap here is that candidates mistakenly add an `else` to a filter-only comprehension, expecting it to work like a ternary operator.
Trap categories for this question
Keyword trap
Invalid syntax: 'then' is not a keyword in list comprehensions.
Detailed technical explanation
List comprehensions in Python are syntactic sugar for building lists from iterables, and they support two forms: filtering (`[expr for item in iterable if condition]`) and conditional expressions (`[expr1 if condition else expr2 for item in iterable]`). Mixing these forms incorrectly, such as appending `else` after a filter `if`, raises a `SyntaxError`. In real-world data pipelines, this pattern is common for cleaning and transforming sensor data, where filtering invalid readings before conversion prevents errors like division by zero or unrealistic values.
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.
What to study next
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FAQ
Control Flow, Loops, Lists and Logic — This question tests Control Flow, Loops, Lists and Logic — Read the scenario before looking for a memorised answer..
The correct answer is: [t*9/5+32 for t in temps if t>0] — Option A is correct because it uses the standard list comprehension syntax: `[expression for item in iterable if condition]`. Here, `t*9/5+32` is the expression that converts Celsius to Fahrenheit, `for t in temps` iterates over the list, and `if t>0` filters out temperatures at or below zero. This produces a new list containing only the Fahrenheit equivalents of positive Celsius temperatures.
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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