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.
Exhibit
Refer to the exhibit.
Error output:
Traceback (most recent call last):
File "script.py", line 3, in <module>
result = value + 10
TypeError: can only concatenate str (not "int") to str
A developer sees the above error. Which line of code likely caused it?
Refer to the exhibit.
Error output:
Traceback (most recent call last):
File "script.py", line 3, in <module>
result = value + 10
TypeError: can only concatenate str (not "int") to str
A
value = eval(input("Enter a number: "))
Why wrong: eval() interprets input as code, but risky; would not cause this error if input is number.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
value = input("Enter a number: ")
Option D is correct because the error shown is a `ValueError` that occurs when the `input()` function returns a string that cannot be converted to a number. The code `value = input("Enter a number: ")` does not attempt any conversion, so it will not raise a `ValueError`; instead, it stores the raw string. The error must have been caused by one of the other options that attempts an explicit type conversion on a non-numeric string.
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.
✗
value = eval(input("Enter a number: "))
Why it's wrong here
eval() interprets input as code, but risky; would not cause this error if input is number.
✗
value = float(input("Enter a number: "))
Why it's wrong here
Convert to float, no error.
✗
value = int(input("Enter a number: "))
Why it's wrong here
Convert to int, no error.
✓
value = input("Enter a number: ")
Why this is correct
input() returns a string, causing the TypeError.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the error is caused by a missing conversion (option D), but the `ValueError` is actually triggered by an *attempted* conversion that fails, so the line without conversion (D) is the only one that would not raise that error.
Detailed technical explanation
How to think about this question
The `ValueError` in Python is raised when a built-in operation or function receives an argument with the correct type but an inappropriate value, such as converting a non-numeric string to `int` or `float`. Under the hood, `int()` and `float()` call the C-level `PyNumber_Int` or `PyFloat_FromString` functions, which parse the string according to strict numeric literal rules (e.g., no leading/trailing spaces, no extra characters). In real-world scenarios, this often occurs when user input contains commas, currency symbols, or whitespace, requiring sanitization before conversion.
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 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
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: value = input("Enter a number: ") — Option D is correct because the error shown is a `ValueError` that occurs when the `input()` function returns a string that cannot be converted to a number. The code `value = input("Enter a number: ")` does not attempt any conversion, so it will not raise a `ValueError`; instead, it stores the raw string. The error must have been caused by one of the other options that attempts an explicit type conversion on a non-numeric string.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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