Question 1

Filtering with if

Accepted Answer

The if clause at the end of a comprehension acts as a filter — only elements where the condition is True are included. x % 2 == 0 is True for 2, 4, and 6. This is equivalent to a for loop with an if block inside, but expressed in one line.

Question 2

List comprehension basics

Accepted Answer

range(4) produces 0, 1, 2, 3. The comprehension multiplies each value by 2, giving [0, 2, 4, 6]. List comprehensions are the idiomatic Python replacement for a for loop that builds a new list — shorter and often faster than append().

Question 3

Dict comprehension

Accepted Answer

A dict comprehension uses curly braces with a key: value expression. {w: len(w) for w in words} maps each word to its length. Dict comprehensions are the clean way to build a dictionary from an iterable without calling dict() on a list of tuples.

Question 4

Set comprehension deduplicates

Accepted Answer

A set comprehension uses curly braces without a colon. Sets discard duplicates, so {1, 2, 2, 3, 3, 3} becomes {1, 2, 3} — length 3. Use a set comprehension when you want unique values from an iterable. The order of elements in the resulting set is not guaranteed.

Question 5

Set comprehension from a string

Accepted Answer

Iterating over a string yields individual characters. 'mississippi' contains 'm', 'i', 's', and 'p' — 4 distinct characters. The set comprehension collects all characters from the string and automatically discards duplicates. This is the idiomatic way to count or inspect unique characters in a string.