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 is working on a project that requires handling large numbers. They write:
x = 10000000000
y = 3.0
z = x / y
print(int(z))
The output is 3333333333. However, the developer expected 3333333333 (same). But they suspect that integer division might be better. They try:
x = 10000000000
y = 3
z = x // y
print(z)
Output: 3333333333. Both give same. Now they test with negative numbers:
x = -10
y = 3
z1 = x / y
z2 = x // y
print(z1, z2)
The output is -3.3333333333333335 and -4. The developer is confused why z2 is -4 instead of -3. Which of the following explains the behavior?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Floor division always rounds down toward negative infinity, so -10 // 3 = -4 because -3.33 floor is -4.
Option C is correct because Python's floor division (`//`) always rounds down toward negative infinity, not toward zero. For `-10 // 3`, the exact result is approximately -3.333..., and the floor (largest integer ≤ the value) is -4, not -3. This is consistent with the mathematical definition of floor division used in Python.
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 operator / rounds toward zero, while // rounds toward negative infinity.
Why it's wrong here
/ performs true division and returns a float; it does not round.
✗
Truncation division always rounds toward zero, so -10 // 3 should be -3, but Python has a bug.
Why it's wrong here
Python's // does not truncate toward zero; it floors.
✓
Floor division always rounds down toward negative infinity, so -10 // 3 = -4 because -3.33 floor is -4.
Why this is correct
Floor division rounds to the nearest integer less than or equal to the exact quotient.
Related concept
Read the scenario before looking for a memorised answer.
✗
The result depends on the types; using float y yields different result.
Why it's wrong here
In the second test, both are ints, so type is not the cause.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the distinction between truncation toward zero (common in many languages) and floor division toward negative infinity (Python's behavior), trapping candidates who assume `//` always rounds toward zero.
Detailed technical explanation
How to think about this question
Under the hood, Python's `//` operator implements floor division by calling `__floordiv__`, which computes `math.floor(a / b)` for integers, ensuring consistent behavior across positive and negative operands. This differs from C or Java, where integer division truncates toward zero. In real-world scenarios like indexing circular buffers or calculating pagination offsets, using `//` with negative numbers can prevent off-by-one errors when moving backward through a list.
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: Floor division always rounds down toward negative infinity, so -10 // 3 = -4 because -3.33 floor is -4. — Option C is correct because Python's floor division (`//`) always rounds down toward negative infinity, not toward zero. For `-10 // 3`, the exact result is approximately -3.333..., and the floor (largest integer ≤ the value) is -4, not -3. This is consistent with the mathematical definition of floor division used in Python.
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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