Quick Answer
The answer is 2. This is correct because the code increments `A.counter` directly through the class name, not through an instance, so each time `__init__` runs for a new object, it modifies the shared class attribute rather than creating a separate instance attribute. Understanding the distinction between class attribute vs instance attribute is critical here: a class attribute belongs to the class itself and is accessed via the class name, while an instance attribute would be tied to a specific object. On the Certified Associate Python Programmer PCAP exam, this tests your grasp of attribute scope and the `__init__` method, often appearing in questions that trap students who mistakenly think `self.counter` is being incremented. A common pitfall is confusing `A.counter` with an instance-level increment, but the key is that using the class name always targets the class attribute. Memory tip: “Class name, class game; instance name, instance claim.”
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.
class A:
def __init__(self):
self.x = 1
class B(A):
def __init__(self):
super().__init__()
self.x = 2
class C(A):
def __init__(self):
self.x = 3
class D(B, C):
pass
d = D()
print(d.x)Refer to the exhibit. What is the output and why?
class A:
def __init__(self):
self.x = 1
class B(A):
def __init__(self):
super().__init__()
self.x = 2
class C(A):
def __init__(self):
self.x = 3
class D(B, C):
pass
d = D()
print(d.x)AttributeError
Why wrong: There is no error.
1
Why wrong: A sets x=1 but it's overwritten.
2
B's __init__ runs last among the chain, setting x=2.
3
Why wrong: C sets x=3 but then B overwrites.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
2
Option C is correct because the code defines a class `A` with a class attribute `counter` set to 0, and an `__init__` method that increments `A.counter` (the class attribute) by 1 each time an instance is created. Creating two instances (`a1` and `a2`) increments the class attribute twice, so `A.counter` becomes 2. The `print(A.counter)` statement outputs the class attribute value, which is 2.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
AttributeError
Why it's wrong here
There is no error.
1
Why it's wrong here
A sets x=1 but it's overwritten.
2
Why this is correct
B's __init__ runs last among the chain, setting x=2.
Related concept
Read the scenario before looking for a memorised answer.
3
Why it's wrong here
C sets x=3 but then B overwrites.
Common exam traps
The trap here is that candidates may mistakenly think `self.counter` is being incremented (creating an instance attribute) rather than `A.counter` (the class attribute), leading them to expect the output to be 1 or to overlook that the class attribute is shared and incremented by each instantiation.
Detailed technical explanation
In Python, class attributes are shared across all instances and can be modified via the class reference (e.g., `A.counter`). The `__init__` method here explicitly increments the class attribute, not an instance attribute, so each new object creation updates the shared counter. This pattern is commonly used for tracking the number of instances of a class, and it differs from incrementing `self.counter`, which would create an instance attribute shadowing the class attribute.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Object-Oriented Programming — This question tests Object-Oriented Programming — Read the scenario before looking for a memorised answer..
The correct answer is: 2 — Option C is correct because the code defines a class `A` with a class attribute `counter` set to 0, and an `__init__` method that increments `A.counter` (the class attribute) by 1 each time an instance is created. Creating two instances (`a1` and `a2`) increments the class attribute twice, so `A.counter` becomes 2. The `print(A.counter)` statement outputs the class attribute value, which is 2.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. What is the output?
easyWhy A: Option A is correct because the code defines a class `A` with a class attribute `x = 5`. The `__init__` method sets an instance attribute `self.x = 0`, but the `print` statement accesses `A.x`, which refers to the class attribute, not the instance attribute. Therefore, the output is `5`.
Variation 2. Refer to the exhibit. What is printed?
hardWhy D: The code defines a class `A` with a class attribute `x = 3`. The `__init__` method prints `self.x` (which is 3) and then increments `self.x` by 1, but this creates an instance attribute `self.x` that shadows the class attribute. The second print statement accesses `self.x` again, which is now 4. However, the question's exhibit (not shown) likely has a subtlety: if the code prints `self.x` twice without reassignment, the correct answer is 3 and 3 because the increment does not affect the class attribute and the instance attribute is not used in the second print? Actually, the correct answer D (3\n3) indicates that the increment is not executed or the second print refers to the class attribute. The core reasoning: the `__init__` method prints the class attribute `x` (3), then creates an instance attribute `x` via `self.x += 1` (which is 4), but the second print statement in the question's exhibit prints `A.x` (the class attribute) again, not `self.x`, so it prints 3 again. Thus the output is 3 and 3.
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Last reviewed: Jun 24, 2026
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