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

`dict.get(key, default)` returns the default value when the key is not found, so 99 is returned.

Question 2

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

Accepted Answer

.pop()

Answer

`dict.pop(key)` removes the key and returns its value, raising KeyError if the key does not exist (unless a default is provided).

Question 3

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

Accepted Answer

Does nothing silently

Answer

`set.discard()` removes the element if present but does nothing if the element is absent, unlike `set.remove()` which raises KeyError.

Question 4

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

Accepted Answer

{2, 3}

Answer

The `&` operator computes set intersection, returning only elements common to both sets.

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

In Python 3.9+, the `|` operator merges two dicts, with the right operand's values winning on duplicate keys.

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