The answer is that __getattribute__ is called, and __getattr__ is not called when accessing an attribute that exists in the instance. This is because Python’s attribute access order always invokes __getattribute__ first for every attribute lookup, regardless of whether the attribute exists. If the attribute is found in the instance dictionary or via a descriptor, __getattribute__ returns it directly, and __getattr__—which only acts as a fallback—is never triggered. On the Certified Associate Python Programmer PCAP exam, this concept tests your understanding of Python’s method resolution for attribute access, often appearing as a trick question where students mistakenly think __getattr__ runs for existing attributes. A common trap is confusing __getattr__ with __getattribute__; remember that __getattr__ is only called when __getattribute__ raises an AttributeError. For a quick memory tip: think of __getattribute__ as the “always-on guard” and __getattr__ as the “emergency backup” that only activates when the guard fails.
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.
When a class defines both __getattr__ and __getattribute__, which one is called when accessing an attribute that exists in the instance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
__getattribute__ is called, and __getattr__ is not called.
In Python, when both __getattr__ and __getattribute__ are defined in a class, __getattribute__ is always called first for every attribute access. If the attribute exists in the instance (e.g., in the instance dictionary or via a descriptor), __getattribute__ returns it directly, and __getattr__ is never invoked. __getattr__ is only called as a fallback when __getattribute__ raises an AttributeError. Therefore, for an existing attribute, only __getattribute__ runs, making option D correct.
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.
✗
__getattr__ always overrides __getattribute__.
Why it's wrong here
__getattr__ is only called when __getattribute__ raises AttributeError.
✗
Both __getattr__ and __getattribute__ are called, in that order.
Why it's wrong here
Only __getattribute__ is called if the attribute exists.
✗
Only __getattr__ is called.
Why it's wrong here
__getattribute__ is the primary hook.
✓
__getattribute__ is called, and __getattr__ is not called.
Why this is correct
For existing attributes, __getattribute__ returns the value directly.
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 __getattr__ is the primary hook for attribute access, when in fact __getattribute__ is always called first and __getattr__ is only a fallback for missing attributes.
Detailed technical explanation
How to think about this question
Under the hood, __getattribute__ is the universal attribute lookup hook that Python calls for every attribute access (e.g., obj.attr). It first checks the instance __dict__, then the class and its bases, and invokes descriptors if present. If the attribute is found, it returns the value without ever calling __getattr__. Only if __getattribute__ raises an AttributeError does Python then call __getattr__ as a last resort. This design allows __getattr__ to serve as a dynamic fallback for missing attributes, while __getattribute__ controls all access, which is critical when implementing proxies or computed attributes.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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: __getattribute__ is called, and __getattr__ is not called. — In Python, when both __getattr__ and __getattribute__ are defined in a class, __getattribute__ is always called first for every attribute access. If the attribute exists in the instance (e.g., in the instance dictionary or via a descriptor), __getattribute__ returns it directly, and __getattr__ is never invoked. __getattr__ is only called as a fallback when __getattribute__ raises an AttributeError. Therefore, for an existing attribute, only __getattribute__ runs, making option D correct.
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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This PCAP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCAP exam.
Question Discussion
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