PCEP Practice Question: Data Types, Variables, Basic I/O and Operators
This PCEP practice question tests your understanding of data types, variables, basic i/o and operators. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 calculate the average of three test scores entered by a user. The scores are integers. The programmer writes the following code:
When run, the output is incorrect. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The input() function returns strings, so concatenation occurs instead of addition.
Option D is correct because the `input()` function in Python always returns a string, even when the user types numbers. The `+` operator on strings performs concatenation (e.g., '5' + '3' + '2' becomes '532'), not numeric addition. Dividing the concatenated string by 3 then causes a `TypeError` (or produces an incorrect result if the string is implicitly converted), so the average calculation fails.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The division by 3 will cause a ZeroDivisionError because 3 is not a float.
Why it's wrong here
Division by 3 is valid and does not cause an error.
✗
The division operator / always returns an integer, but the sum is not an integer.
Why it's wrong here
In Python, / returns a float, not an integer.
✗
The variable names s1, s2, s3 are not allowed because they start with a letter.
Why it's wrong here
Variable names can start with a letter.
✓
The input() function returns strings, so concatenation occurs instead of addition.
Why this is correct
input() returns a string, so using + on strings concatenates them.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the misconception that `input()` returns a numeric type, leading candidates to overlook the need for explicit type conversion before arithmetic operations.
Detailed technical explanation
How to think about this question
Under the hood, `input()` reads from stdin and returns a string object. When you use `+` on strings, Python invokes the `__add__` method of the string class, which concatenates. To perform numeric addition, you must explicitly convert each input to an integer using `int()` or `float()`. In real-world applications, failing to cast user input is a common source of bugs, especially when processing CSV data or form submissions where values arrive as strings.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Types, Variables, Basic I/O and Operators — This question tests Data Types, Variables, Basic I/O and Operators — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The input() function returns strings, so concatenation occurs instead of addition. — Option D is correct because the `input()` function in Python always returns a string, even when the user types numbers. The `+` operator on strings performs concatenation (e.g., '5' + '3' + '2' becomes '532'), not numeric addition. Dividing the concatenated string by 3 then causes a `TypeError` (or produces an incorrect result if the string is implicitly converted), so the average calculation fails.
What should I do if I get this PCEP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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