PCAP Object-Oriented Programming Practice Question
This PCAP practice question tests your understanding of object-oriented programming. 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 is developing a scientific simulation framework where many different solvers must be interchangeable. The framework should enforce that each solver implements methods 'initialize' and 'step'. Developers want to use abstract base classes. Which approach should the team take to ensure that any subclass of 'Solver' cannot be instantiated unless it defines both methods?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Inherit from ABC and decorate both methods with @abstractmethod
Option C is correct because inheriting from `ABC` (from the `abc` module) and decorating both `initialize` and `step` with `@abstractmethod` enforces that any concrete subclass must override these methods. Attempting to instantiate a subclass that does not implement all abstract methods raises a `TypeError`, ensuring compile-time-like safety at runtime.
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.
✗
Define an interface in a separate module and check using isinstance
Why it's wrong here
Python does not have native interface types; ABC is the recommended approach.
✗
Use @abstractmethod without inheriting from ABC
Why it's wrong here
Without ABC inheritance, @abstractmethod has no effect; the class can be instantiated.
✓
Inherit from ABC and decorate both methods with @abstractmethod
Why this is correct
This enforces that subclasses must provide implementations; they cannot be instantiated otherwise.
Related concept
Read the scenario before looking for a memorised answer.
✗
Define Solver with methods that raise NotImplementedError
Why it's wrong here
This does not prevent instantiation; it only raises error when the method is called.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the misconception that `@abstractmethod` alone (without inheriting from `ABC`) is sufficient to prevent instantiation, or that raising `NotImplementedError` is equivalent to abstract base class enforcement.
Detailed technical explanation
How to think about this question
Under the hood, `ABC` uses `ABCMeta` as its metaclass, which tracks abstract methods via `__abstractmethods__`. When a class is instantiated, Python checks this set; if any abstract methods remain unimplemented, it raises `TypeError: Can't instantiate abstract class ... with abstract methods ...`. This mechanism is part of PEP 3119 and is distinct from duck typing — it provides a formal contract for frameworks where interchangeable components must guarantee certain interfaces.
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: Inherit from ABC and decorate both methods with @abstractmethod — Option C is correct because inheriting from `ABC` (from the `abc` module) and decorating both `initialize` and `step` with `@abstractmethod` enforces that any concrete subclass must override these methods. Attempting to instantiate a subclass that does not implement all abstract methods raises a `TypeError`, ensuring compile-time-like safety at runtime.
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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