[Effective Python] WAY 8. 리스트 컴프리헨션에서 표현식을 두 개 넘게 쓰지 말자

matrix = [[1, 2, 3], [4, 5, 6]]
flat = [x for row in matrix for x in row]
print(flat)

>>>
[1, 2, 3, 4, 5, 6]

matrix = [[1, 2, 3], [4, 5, 6]]
flat = []
for row in matrix:
    for x in row:
        flat.append(x)

matrix = [[1, 2, 3], [4, 5, 6]]
squared = [[x**2 for x in row] for row in matrix]
print(squared)

>>>
[[1, 4, 9], [16, 25, 36]]

my_lists = [
    [[1, 2, 3], [4, 5, 6]],
    # ...
]
flat = [x for sublist1 in my_lists
        for sublist2 in sublist1
        for x in sublist2]

flat = []
for sublist1 in my_lists:
    for sublist2 in sublist1:
        flat.extend(sublist2)

a = [1, 2, 3, 4, 5, 6]
b = [x for x in a if x > 4 if x % 2 == 0]
c = [x for x in a if x > 4 and x % 2 == 0]

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
filtered = [[x for x in row if x % 3 == 0]
            for row in matrix if sum(row) >= 10]
print(filtered)

>>>
[[6], [9]]