Python Data Structures: Dictionaries and Sets 4

Question 1

What does `{} == set()` evaluate to?

Accepted Answer

False

Answer

`{}` creates an empty dictionary, not an empty set; `set()` creates an empty set, so they are not equal.

Question 2

Given `d = {'x': 10, 'y': 20}`, what is `list(d)`?

Accepted Answer

['x', 'y']

Answer

Iterating over a dictionary yields its keys, so `list(d)` produces a list of keys.

Question 3

What is the output of `s = {3, 1, 2}; print(min(s))`?

Accepted Answer

1

Answer

`min()` works on any iterable including sets and returns the smallest element, which is 1.

Question 4

What does `{1, 2, 3} - {2, 3, 4}` return?

Accepted Answer

{1}

Answer

The `-` operator on sets returns the difference: elements in the left set that are not in the right set.

Question 5

Which approach creates a dictionary from two lists `keys` and `values`?

Accepted Answer

dict(zip(keys, values))

Answer

`zip(keys, values)` pairs elements together and `dict()` converts those pairs into a dictionary.

Python Practice Test