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. 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 writes code to compute the average of two numbers entered by the user: x = input('Enter first number: '); y = input('Enter second number: '); avg = (x + y) / 2. The program produces an error. What is the best practice to fix the code?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Convert the result to int after the operation: avg = int((x + y) / 2)
Why wrong: This does not solve the string concatenation issue; x + y would concatenate strings.
B
Use int() on the input() values: x = int(input(...)); y = int(input(...))
Why wrong: This works only if the input is a whole number, but the problem does not specify integers.
C
Use type casting in the division: avg = (float(x) + float(y)) / 2
Why wrong: This would work but is less efficient than converting once; however, the order is correct, so this could also work but is not best practice because it repeats conversion.
D
Convert x and y to float before the operation: x = float(input(...)); y = float(input(...))
This ensures the addition and division work on numeric values.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Convert x and y to float before the operation: x = float(input(...)); y = float(input(...))
Option D is correct because the `input()` function in Python always returns a string. When you use the `+` operator on two strings, it concatenates them (e.g., '5' + '3' = '53'), not adds them numerically. Dividing a concatenated string by 2 raises a TypeError. The best practice is to convert both inputs to `float` immediately after receiving them, ensuring the subsequent arithmetic works correctly.
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.
✗
Convert the result to int after the operation: avg = int((x + y) / 2)
Why it's wrong here
This does not solve the string concatenation issue; x + y would concatenate strings.
✗
Use int() on the input() values: x = int(input(...)); y = int(input(...))
Why it's wrong here
This works only if the input is a whole number, but the problem does not specify integers.
✗
Use type casting in the division: avg = (float(x) + float(y)) / 2
Why it's wrong here
This would work but is less efficient than converting once; however, the order is correct, so this could also work but is not best practice because it repeats conversion.
✓
Convert x and y to float before the operation: x = float(input(...)); y = float(input(...))
Why this is correct
This ensures the addition and division work on numeric values.
Clue confirmation
The clue words "best", "first" 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 pick Option B (using `int`) or Option C (casting inside the expression), but the trap is that string concatenation happens before any conversion, so the error occurs at the `+` operator, not at the division.
Detailed technical explanation
How to think about this question
Under the hood, Python's `input()` returns a `str` object. The `+` operator is overloaded: for strings it performs concatenation, for numbers it performs addition. By converting to `float` immediately, you change the object type to a numeric type, enabling arithmetic. In real-world scenarios, such as averaging sensor readings, failing to cast inputs leads to silent data corruption (e.g., '12' + '34' = '1234') rather than an error, making debugging harder.
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: Convert x and y to float before the operation: x = float(input(...)); y = float(input(...)) — Option D is correct because the `input()` function in Python always returns a string. When you use the `+` operator on two strings, it concatenates them (e.g., '5' + '3' = '53'), not adds them numerically. Dividing a concatenated string by 2 raises a TypeError. The best practice is to convert both inputs to `float` immediately after receiving them, ensuring the subsequent arithmetic works correctly.
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: "best", "first". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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