- A
Tuple
Why wrong: Tuples are immutable and membership tests are O(n).
- B
Set
Sets are designed for unique elements and fast membership testing.
- C
List
Why wrong: Lists can contain duplicates and membership tests are O(n).
- D
Dictionary
Why wrong: Dictionaries store key-value pairs; membership tests on keys are fast, but storing only values would waste memory.
Question 919 of 1,000
200-901 Software Development and Design Practice Question
This 200-901 practice question tests your understanding of software development and design. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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.
Which data structure in Python would be most appropriate for storing a collection of unique items and performing fast membership tests?
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
✓
Set
A set is the correct choice because it is implemented as a hash table in Python, which provides O(1) average-time complexity for membership tests using the `in` operator. Sets automatically enforce uniqueness, meaning duplicate items are not allowed, making them ideal for storing a collection of distinct elements. This directly matches the requirement for fast membership testing and uniqueness.
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.
- ✗
Tuple
Why it's wrong here
Tuples are immutable and membership tests are O(n).
- ✓
Set
Why this is correct
Sets are designed for unique elements and fast membership testing.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
List
Why it's wrong here
Lists can contain duplicates and membership tests are O(n).
- ✗
Dictionary
Why it's wrong here
Dictionaries store key-value pairs; membership tests on keys are fast, but storing only values would waste memory.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a dictionary is the best choice for fast membership tests because it also uses hashing, but the trap is that the question specifically asks for a collection of unique items, not key-value pairs, making a set the more precise and appropriate data structure.
Detailed technical explanation
How to think about this question
Under the hood, Python sets use a hash table with open addressing, where each element's hash determines its bucket; this ensures O(1) average-case lookup but O(n) worst-case if many hash collisions occur. A subtle behavior is that sets require all elements to be hashable (immutable), so you cannot store lists or dictionaries inside a set, but you can store tuples. In real-world scenarios, sets are commonly used for deduplication of data streams or for fast intersection/union operations in network automation scripts, such as comparing IP address lists from different sources.
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 practitioner preparing for the 200-901 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
- →
Software Development and Design — study guide chapter
Learn the concepts, then practise the questions
- →
Software Development and Design practice questions
Targeted practice on this topic area only
- →
All 200-901 questions
1,000 questions across all exam domains
- →
Cisco DevNet Associate 200-901 study guide
Full concept coverage aligned to exam objectives
- →
200-901 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 200-901 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Software Development and Design practice questions
Practise 200-901 questions linked to Software Development and Design.
Understanding and Using APIs practice questions
Practise 200-901 questions linked to Understanding and Using APIs.
Application Deployment and Security practice questions
Practise 200-901 questions linked to Application Deployment and Security.
Cisco Platforms and Development practice questions
Practise 200-901 questions linked to Cisco Platforms and Development.
Network Fundamentals practice questions
Practise 200-901 questions linked to Network Fundamentals.
Infrastructure and Automation practice questions
Practise 200-901 questions linked to Infrastructure and Automation.
200-901 fundamentals practice questions
Practise 200-901 questions linked to 200-901 fundamentals.
200-901 scenario practice questions
Practise 200-901 questions linked to 200-901 scenario.
200-901 troubleshooting practice questions
Practise 200-901 questions linked to 200-901 troubleshooting.
Practice this exam
Start a free 200-901 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 200-901 question test?
Software Development and Design — This question tests Software Development and Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set — A set is the correct choice because it is implemented as a hash table in Python, which provides O(1) average-time complexity for membership tests using the `in` operator. Sets automatically enforce uniqueness, meaning duplicate items are not allowed, making them ideal for storing a collection of distinct elements. This directly matches the requirement for fast membership testing and uniqueness.
What should I do if I get this 200-901 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This 200-901 practice question is part of Courseiva's free Cisco 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 200-901 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.