Question

I want a list full of the same thing, where the thing will either be a string or a number. Is there a difference in the way these two list are created? Is there anything hidden that I should probably know about?

list_1 = [0] * 10

list_2 = [0 for i in range(10)]

Are there any better ways to do this same task?

Thanks in advance.

Answer 1

It depends on whether your list elements are mutable, if they are, there’ll be a difference:

>>> l = [[]] * 10
>>> l
[[], [], [], [], [], [], [], [], [], []]
>>> l[0].append(1)
>>> l
[[1], [1], [1], [1], [1], [1], [1], [1], [1], [1]]
>>> l = [[] for i in range(10)]
>>> l[0].append(1)
>>> l
[[1], [], [], [], [], [], [], [], [], []]

For immutable elements, the behavior of the two is the same. There might be a performance difference between them, but I’m not sure which one would perform faster.