The correct choice is the code snippet that uses the `@property` decorator with only a getter method, such as `class Temperature: @property def celsius(self): return self._celsius`. This works because the `@property` decorator transforms the method into a read-only property by default; without a corresponding setter, any attempt to assign a value to `celsius` raises an `AttributeError`, preventing external modification. On the Certified Associate Python Programmer PCAP exam, this concept tests your understanding of encapsulation and the property decorator’s role in controlling attribute access—a common trap is assuming you need a setter to make a property read-only, when in fact omitting the setter is the key. The exam often presents distractors that include a setter or use a plain attribute without `@property`, so remember: no setter means no write access. Memory tip: “Getter only, property holy—no setter, no rewrite.”
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 wants to implement a read-only property for a class 'Temperature' that returns the temperature in Celsius but prevents external modification. Which code snippet correctly defines such a property?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
class Temperature: @property
def celsius(self): return self._celsius
Option C is correct because it defines a read-only property using the `@property` decorator with only a getter method. Without a setter, any attempt to assign a value to `celsius` will raise an `AttributeError`, making the property read-only. This is the standard Pythonic way to implement a read-only attribute.
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.
✗
class Temperature: @property
def celsius(self): return self._celsius
@celsius.setter
def celsius(self, val): self._celsius = val
Why it's wrong here
This allows external modification via the setter.
✗
class Temperature: def __setattr__(self, name, val): if name == 'celsius': raise AttributeError
Why it's wrong here
This prevents all attribute setting, not a proper property implementation.
✓
class Temperature: @property
def celsius(self): return self._celsius
Why this is correct
This defines a getter only, making the property read-only.
Related concept
Read the scenario before looking for a memorised answer.
✗
class Temperature: def __init__(self, c): self.celsius = c
Why it's wrong here
This is a regular attribute, not a read-only property.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the misconception that a property without a setter is still writable by default, or that overriding `__setattr__` is a valid alternative to `@property` for creating a read-only attribute, but the correct approach is to omit the setter decorator entirely.
Detailed technical explanation
How to think about this question
Under the hood, `@property` creates a descriptor object that intercepts attribute access. When only a getter is defined, the descriptor's `__set__` method is not implemented, so Python's attribute lookup falls back to the instance dictionary, but the descriptor takes precedence on access; any assignment triggers `AttributeError` because the descriptor lacks a setter. This pattern is commonly used in data validation or caching scenarios where computed attributes must be immutable after initialization.
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: class Temperature: @property
def celsius(self): return self._celsius — Option C is correct because it defines a read-only property using the `@property` decorator with only a getter method. Without a setter, any attempt to assign a value to `celsius` will raise an `AttributeError`, making the property read-only. This is the standard Pythonic way to implement a read-only attribute.
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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