PCPP2 Design Patterns Practice Question
You are implementing the Visitor pattern to add operations to a set of stable class structures. Why is the 'Double Dispatch' mechanism essential?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It resolves the method call based on the runtime types of both the visitor and the element
Double dispatch ensures that the correct method is executed based on both the type of the Visitor and the type of the Element being visited.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It prevents the element from needing to know about the visitor
Why it's wrong here
The element must have an 'accept' method that knows about the visitor interface.
- ✗
It allows the visitor to access private methods of the element
Why it's wrong here
Visitor does not override access control.
- ✓
It resolves the method call based on the runtime types of both the visitor and the element
Why this is correct
This is the core concept of double dispatch in the Visitor pattern.
- ✗
It allows the visitor to be defined as a singleton
Why it's wrong here
Visitor pattern does not require Singletons.
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Last reviewed August 2026 · checked against the official Python Institute exam blueprint
This PCPP2 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 PCPP2 exam.