Python Data Structures: Dictionaries and Sets 3

Question 1

What is the output of `d = {}; d[('a', 'b')] = 1; print(len(d))`?

Accepted Answer

1

Answer

Tuples are hashable and can be used as dictionary keys; the dictionary has one key-value pair so its length is 1.

Question 2

Which expression produces a frozenset?

Accepted Answer

frozenset([1, 2, 3])

Answer

`frozenset()` accepts an iterable and returns an immutable, hashable set.

Question 3

What does `{k: v for k, v in [('a', 1), ('b', 2)]}` produce?

Accepted Answer

{'a': 1, 'b': 2}

Answer

This dict comprehension unpacks each two-element tuple into key-value pairs, building a dictionary.

Question 4

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

Accepted Answer

{1, 2, 3, 4}

Answer

The `|` operator on sets returns the union — all elements from both sets with no duplicates.

Question 5

Which statement about Python dictionaries is TRUE as of Python 3.7+?

Accepted Answer

Insertion order is preserved

Answer

Since Python 3.7, dictionaries maintain insertion order as part of the language specification.

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