Python List Dict Tuple Interview Questions 2026: 28 Q&A

Last Updated: June 2026 | Level: Freshers to Mid-Level | Read Time: ~15 min

Lists, dicts, and tuples are the three containers every Python interview touches. Candidates report that mutability, comprehensions, dict methods, and unpacking are guaranteed screening topics. This guide covers 28 focused questions with full answers and predict-the-output traps that interviewers use to catch shallow understanding. Behaviour reflects the official Python documentation; confirm any method-level detail on the official docs.

Pair this with Python Interview Questions 2026 and Python Data Structures Interview Questions 2026.

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Table of Contents

1. Lists (Q1 to Q10)
2. Tuples (Q11 to Q16)
3. Dicts (Q17 to Q25)
4. Cross-Container (Q26 to Q28)
5. Predict the Output
6. Method Cheat Sheet
7. Frequently Asked Questions

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Lists

Q1. How is a list stored in memory? Medium

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Q2. What is the difference between remove, pop, and del for lists? Medium

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Q3. How do you flatten a nested list? Medium

nested = [[1, 2], [3, 4]]
flat = [x for sub in nested for x in sub]   # [1, 2, 3, 4]

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Q4. How do you remove duplicates while preserving order? Medium

unique = list(dict.fromkeys([3, 1, 3, 2, 1]))  # [3, 1, 2]

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Q5. What does list multiplication do with nested lists? Hard

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Q6. What is the difference between a list comprehension and a generator expression? Medium

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Q7. How do you sort a list of tuples by the second element? Medium

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Q8. What does enumerate do? Easy

for i, v in enumerate(["a", "b"], 1):
    print(i, v)        # 1 a / 2 b

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Q9. What does zip do and how do you reverse it? Medium

pairs = list(zip([1, 2], ["a", "b"]))   # [(1,'a'), (2,'b')]
nums, letters = zip(*pairs)

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Q10. What is the difference between is and == for lists? Medium

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Tuples

Q11. Why use a tuple instead of a list? Easy

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Q12. How do you create a single-element tuple? Easy

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Q13. Can you sort a tuple? Medium

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Q14. What is tuple unpacking and swapping? Easy

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Q15. Are tuples always hashable? Hard

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Q16. What is a named tuple and when to use it? Medium

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Dicts

Q17. What are the main ways to iterate a dict? Easy

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Q18. What is the difference between get and indexing for dicts? Easy

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Q19. What does setdefault do? Medium

d = {}
d.setdefault("a", []).append(1)   # {'a': [1]}

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Q20. How do you merge two dicts? Medium

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Q21. How do you invert a dict? Medium

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Q22. What does dict.items() return and is it a copy? Hard

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Q23. Why must dict keys be hashable? Medium

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Q24. How do you count word frequency with a dict? Medium

freq = {}
for w in words:
    freq[w] = freq.get(w, 0) + 1

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Q25. What happens with duplicate keys in a dict literal? Hard

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Cross-Container

Q26. How do you convert between list, tuple, set, and dict? Easy

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Q27. Which container for which job? Medium

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Q28. How do you sort a dict by value? Medium

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Predict the Output

Snippet 1

grid = [[0] * 3] * 2
grid[0][0] = 9
print(grid)

Output:

[[9, 0, 0], [9, 0, 0]]

Why: The outer * 2 duplicates the same inner-list reference, so setting one row's element changes both. Build rows with a comprehension to avoid this.

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Snippet 2

d = {"a": 1, "b": 2}
for k in d:
    print(k, end=" ")
print()
print(list(d.values()))

Output:

a b 
[1, 2]

Why: Dicts preserve insertion order since 3.7, so iteration and values follow insertion order.

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Snippet 3

t = (1, 2)
print(t * 2)
print((5))
print((5,))

Output:

(1, 2, 1, 2)
5
(5,)

Why: * repeats a tuple. (5) is just the int 5; only the trailing comma makes a one-element tuple.

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Method Cheat Sheet

Task	List	Dict	Tuple
add item	append / insert	d[k]=v / update	immutable
remove item	remove / pop / del	pop / del	immutable
safe access	n/a	get(k, default)	t[i]
membership	in (O(n))	in (O(1) keys)	in (O(n))
comprehension	[..]	{k: v ..}	use generator + tuple()

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Frequently Asked Questions

What is the most asked list vs tuple question in 2026?

Candidates report that explaining mutability, why a tuple can be a dict key, and the performance difference are the three most repeated angles on list versus tuple.

Are dict methods tested in Python interviews?

Yes. get, setdefault, items, keys, values, update, and the merge operator come up regularly, often with a follow-up on avoiding KeyError safely.

Do interviewers ask comprehension questions?

Frequently. List, dict, and set comprehensions appear, with nested comprehensions and the difference between a generator expression and a list comprehension as common follow-ups.

Why does [[0]*3]*2 cause a bug?

The outer multiplication copies the same inner-list reference, so mutating one row affects all rows. Use [[0]*3 for _ in range(2)] to create independent rows.

How do I make a single-element tuple?

Add a trailing comma, (1,). Without it, (1) is simply the integer 1 in parentheses, which catches many beginners in output questions.

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Related Articles

• Python Interview Questions 2026, the master set
• Python Data Structures Interview Questions 2026, complexity and collections
• Python OOPs Interview Questions 2026, object model
• Python Output Prediction Questions 2026, tricky snippets

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Confirm any method-level behaviour on the official Python documentation before your interview. This guide reflects candidate-reported patterns and public preparation resources as of June 2026.