Python cartesian product: Advanced example of list comprehension

The code shows how to make a cartesian product in Python. This is an advanced example of Python list comprehension.

u = ['A', 'B']
v = ['a', 'b', 'c']

w = [x + y for x in u for y in v]

print(w)
# ['Aa', 'Ab', 'Ac', 'Ba', 'Bb', 'Bc']

Cartesian product is so important in math. If not using Python list comprehension, you may write like this.

u = ['A', 'B']
v = ['a', 'b', 'c']

w = []

for i in u:
    for j in v:
        w.append(i + j)

Of course, it's OK. Which style is better depends on the programmar's or team's preference.