PCAP Object-Oriented Programming Practice Question
This PCAP practice question tests your understanding of object-oriented programming. 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 creates classes `A`, `B(A)`, `C(A)`, and `D(B, C)`. When calling a method from `D` that is defined in `A`, which class's version is used according to Python's MRO?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The method from A, found through B then C.
Python's Method Resolution Order (MRO) for class `D(B, C)` follows the C3 linearization algorithm, which ensures a depth-first left-to-right search while preserving monotonicity. For `D(B, C)`, the MRO is `D -> B -> C -> A`, so a method defined in `A` that is not overridden in `B` or `C` will be found via `B` first, then `C`, and finally `A`. Option D correctly states that the method from `A` is used, found through `B` then `C`, which matches the actual resolution path.
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 method from B, because it is the first parent.
Why it's wrong here
B does not define the method, so MRO continues.
✗
The method from C, because it appears after B.
Why it's wrong here
C also does not define the method.
✗
The method from A, but only if B and C do not override it.
Why it's wrong here
That is true but not the full story; MRO ensures A is reached if neither B nor C define it.
✓
The method from A, found through B then C.
Why this is correct
MRO is D -> B -> C -> A, so the first parent with the method is A after traversing B and C.
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 Python's MRO simply searches the first parent and its ancestors before moving to the next parent (depth-first left-to-right), but the actual C3 linearization can produce a different order, especially in diamond inheritance, and candidates may incorrectly assume the method from `A` is found directly without considering the intermediate classes in the MRO.
Detailed technical explanation
How to think about this question
The C3 linearization algorithm used by Python's MRO ensures that the order respects the local precedence order (parents listed left to right) and monotonicity (a class's MRO is preserved in its subclasses). For `D(B, C)`, the MRO is computed as `D + merge(MRO(B), MRO(C), [B, C])`, which yields `D -> B -> C -> A` because `B` inherits from `A`, `C` inherits from `A`, and `A` has no further bases. This matters in diamond inheritance scenarios where a method is overridden in multiple branches; the MRO determines which version is called, and `super()` in `D` will follow the same order, which can lead to unexpected behavior if developers assume a simple left-to-right parent search.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
Object-Oriented Programming — This question tests Object-Oriented Programming — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The method from A, found through B then C. — Python's Method Resolution Order (MRO) for class `D(B, C)` follows the C3 linearization algorithm, which ensures a depth-first left-to-right search while preserving monotonicity. For `D(B, C)`, the MRO is `D -> B -> C -> A`, so a method defined in `A` that is not overridden in `B` or `C` will be found via `B` first, then `C`, and finally `A`. Option D correctly states that the method from `A` is used, found through `B` then `C`, which matches the actual resolution path.
What should I do if I get this PCAP 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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