Question 374 of 498
PCEP Practice Question: Functions, Tuples, Dictionaries and Exceptions
A programmer needs to store configuration settings keyed by string, where each key maps to a list of allowed values. Which data structure is most appropriate?
⚠ Common exam trap
Python Institute often tests the distinction between data structures that store pairs (like dictionaries) versus those that store sequences (like lists or tuples), and the trap here is that candidates may choose a list of tuples (Option C) because it visually pairs keys and values, but overlook that it lacks the efficient key-based lookup that a dictionary provides.
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
✓
A dictionary where keys are strings and values are lists.
A dictionary in Python provides direct key-to-value mapping, making it ideal for storing configuration settings where each string key must map to a list of allowed values. Dictionaries offer O(1) average-time complexity for lookups, which is efficient for retrieving the list of values for a given key. This structure directly models the requirement without unnecessary nesting or indirection.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A tuple of lists where each list starts with the key.
Why it's wrong here
Tuples are immutable; not ideal for dynamic mapping.
- ✓
A dictionary where keys are strings and values are lists.
Why this is correct
Provides O(1) average key lookup and each key maps to a list of allowed values.
- ✗
A list of tuples where each tuple contains a key and a list of values.
Why it's wrong here
Requires linear search; not efficient for key lookup.
- ✗
A set of strings representing the keys, with a separate list for values.
Why it's wrong here
Cannot associate multiple values per key easily.
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Last reviewed: Jun 30, 2026
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