Python Data Structures: Dictionaries and Sets 2

Question 1

What is the output of `d = {'a': 1, 'b': 2}; print(d.get('c', 99))`?

Accepted Answer

99

Answer

None

Answer

KeyError

Answer

0

Question 2

Which method removes a key from a dictionary and returns its value, raising KeyError if missing?

Accepted Answer

.pop()

Answer

.get()

Answer

.discard()

Answer

.remove()

Question 3

What does `s = {1, 2, 3}; s.discard(5)` do?

Accepted Answer

Does nothing silently

Answer

Raises KeyError

Answer

Raises ValueError

Answer

Adds 5 to the set

Question 4

What is the result of `{1, 2, 3} & {2, 3, 4}`?

Accepted Answer

{2, 3}

Answer

{1, 2, 3, 4}

Answer

{1, 4}

Answer

{1, 2, 3, 2, 3, 4}

Question 5

Which of the following correctly merges dict `b` into dict `a`, overwriting duplicate keys with `b`'s values (Python 3.9+)?

Accepted Answer

a | b

Answer

a.update(b)

Answer

a.merge(b)

Answer

a + b

Question 6

What is the time complexity of checking membership (`x in s`) in a Python set?

Accepted Answer

O(1) average

Answer

O(n)

Answer

O(log n)

Answer

O(n²)

Question 7

What does `dict.setdefault('key', [])` do when 'key' already exists in the dict?

Accepted Answer

Returns the existing value without changing the dict

Answer

Overwrites the existing value with []

Answer

Returns [] without changing the dict

Answer

Raises KeyError