Summary - List comprehension
- Python course
- Beginner
- Lesson 64/116
- 5 min
Combine comprehension and generator expressions to write a number processor.
Summary - List comprehension
In this group we covered comprehension, filtering, dict/set, nested and generator.
- List:
[expr for n in list] - Filter: add
... if condition - Dict:
{key: value for ...} - Set:
{expr for ...} - Generator:
(expr for ...)
Now two tasks combine these concepts.
Practice Squares of even numbers
Assign to even_squares a comprehension that squares the even numbers from [1, 2, 3, 4, 5, 6]. Then print print(even_squares).
Starter code
# Square the even numbers with a comprehensionSample solution
even_squares = [n * n for n in [1, 2, 3, 4, 5, 6] if n % 2 == 0]
print(even_squares)Expected output
[4, 16, 36]
Practice Dict and sum together
Assign to squares a dict comprehension holding n: n * n for each n in [1, 2, 3]. Assign sum(squares.values()) to total. Then print print(squares, total).
Starter code
# Dict comprehension and sum togetherSample solution
squares = {n: n * n for n in [1, 2, 3]}
total = sum(squares.values())
print(squares, total)Expected output
{1: 1, 2: 4, 3: 9} 14
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which comprehension gives [6, 8]?
- [n * 2 for n in [1, 2, 3, 4]]
- [n * 2 for n in [1, 2, 3, 4] if n > 2] Correct answer
- [n + 2 for n in [1, 2, 3, 4] if n > 2]
- [n for n in [6, 8]]
Explanation: 3 and 4 are taken, doubled to [6, 8].
2 Complete max with a generator
Question
biggest = max(n * n for n in [____])
Answer
biggest = max(n * n for n in [5])Explanation: For [1, 2, 3, 4, 5] the largest square is 25.