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 data analyst has a list of temperature readings in Celsius and wants to create a new list containing only readings that are valid (>= -273.15 and <= 1000). Which code correctly creates the filtered list?
valid = [temp for temp in temps if -273.15 <= temp <= 1000]
Correct; uses chained comparison to include boundaries.
valid = [temp for temp in temps if temp > -273.15 and temp < 1000]
Why wrong: Excludes -273.15 and 1000.
valid = [] for t in temps: if t > -273.15 and t < 1000: valid.append(t)
Why wrong: Invalid syntax; missing colon or indentation.
valid = list(filter(lambda t: t >= -273.15, temps))
Why wrong: Only checks lower bound.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
valid = [temp for temp in temps if -273.15 <= temp <= 1000]
Option A is correct because it uses a list comprehension with a chained comparison (`-273.15 <= temp <= 1000`) that correctly includes both boundary values. This syntax is Pythonic and ensures temperatures equal to -273.15 or 1000 are considered valid, matching the requirement exactly.
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.
valid = [temp for temp in temps if -273.15 <= temp <= 1000]
Why this is correct
Correct; uses chained comparison to include boundaries.
Related concept
Read the scenario before looking for a memorised answer.
valid = [temp for temp in temps if temp > -273.15 and temp < 1000]
Why it's wrong here
Excludes -273.15 and 1000.
valid = [] for t in temps: if t > -273.15 and t < 1000: valid.append(t)
Why it's wrong here
Invalid syntax; missing colon or indentation.
valid = list(filter(lambda t: t >= -273.15, temps))
Why it's wrong here
Only checks lower bound.
Common exam traps
Python Institute often tests the distinction between inclusive (`<=`, `>=`) and exclusive (`<`, `>`) comparisons, and the trap here is that candidates may overlook the boundary values or choose a syntactically incorrect loop structure like Option C.
Detailed technical explanation
Chained comparisons in Python, like `-273.15 <= temp <= 1000`, are evaluated as a single expression equivalent to `temp >= -273.15 and temp <= 1000`, but with the advantage that `temp` is evaluated only once. This is a Python-specific feature not found in many other languages, and it improves readability and performance in list comprehensions. In real-world data validation, such as sensor data filtering, inclusive boundaries are critical to avoid discarding valid extreme readings.
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: valid = [temp for temp in temps if -273.15 <= temp <= 1000] — Option A is correct because it uses a list comprehension with a chained comparison (`-273.15 <= temp <= 1000`) that correctly includes both boundary values. This syntax is Pythonic and ensures temperatures equal to -273.15 or 1000 are considered valid, matching the requirement exactly.
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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