DataEngPrep.tech
QuestionsPracticeAI CoachDashboardPacksBlog
ProLogin
Home/Questions/Python/Coding/What is the difference between a set and a list in Python?

What is the difference between a set and a list in Python?

Python/Codingeasy0.4 min read

**List**: Ordered; allows duplicates; indexable; O(n) lookup. **Set**: Unordered; unique elements only; hash-based; O(1) average lookup. **Why it matters**: Set membership and deduplication are fast; lists preserve order and support duplicates. **Scalability trade-off**: Sets...

🤖 Analyze Your Answer
Frequency
Low
Asked at 2 companies
Category
179
questions in Python/Coding
Difficulty Split
127E|24M|28H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
AltimetrikInfosys
Interview Pro Tip

Red Flag: Using a list for membership checks in a loop—O(n²). Pro-Move: 'I use sets for lookups and dedup; for order-preserving dedup I use dict.fromkeys(seq) or OrderedDict.'

Key Concepts Tested
python

Why This Question Matters

This easy-level Python/Coding question appears frequently in data engineering interviews at companies like Altimetrik, Infosys. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (python) will help you answer variations of this question confidently.

How to Approach This

Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.

Expert Answer
83 words

List: Ordered; allows duplicates; indexable; O(n) lookup. Set: Unordered; unique elements only; hash-based; O(1) average lookup. Why it matters: Set membership and deduplication are fast; lists preserve order and support duplicates. Scalability trade-off: Sets use more memory per element (hash + overhead); lists are compact. For large dedup, set wins on lookup; for ordered data, list is required. Cost implication: Repeated x in list is O(n) per check; x in set is O(1). Use sets for membership and uniqueness; lists for ordered sequences.

dataengprep.techdataengprep.techdataengprep.techdataengprep.tech
dataengprep.techdataengprep.techdataengprep.techdataengprep.tech
dataengprep.techdataengprep.techdataengprep.techdataengprep.tech
dataengprep.techdataengprep.techdataengprep.techdataengprep.tech
dataengprep.techdataengprep.techdataengprep.techdataengprep.tech
dataengprep.techdataengprep.techdataengprep.techdataengprep.tech

Want feedback on your answer?

Paste your answer to this question and our AI Coach scores it, finds gaps, and shows you the FAANG-level version.

Try Answer Analyzer →
Want all answers as a PDF for offline study?
1,863 questions across 7 categories — Interview Packs →

Related Python/Coding Questions

easyWhat are traits in Scala, and how are they different from classes?FreemediumWrite a Python function to check if a string is a palindrome.FreeeasyWhat is the difference between a list and a tuple in Python?FreeeasyExplain the difference between shallow copy and deep copy in Python.FreeeasyWrite a Python function to find the first non-repeating character in a string.Free

Companies that ask this Python/Coding question

Altimetrik interview questions →Infosys interview questions →

Want to know if YOUR answer is good enough?

Paste your answer and get instant AI feedback with a FAANG-level improved version.

Analyze My Answer — Free

According to DataEngPrep.tech, this is one of the most frequently asked Python/Coding interview questions, reported at 2 companies. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

← Back to all questionsMore Python/Coding questions →