What does it "-1" in the loop mean

Question

CAPACITY = 10
buffer = [-1 for i in range(CAPACITY)]

It's not a loop, though. It's called a "list comprehension" – Sergio Tulentsev Oct 26 '21 at 16:15 — Sergio Tulentsev, Oct 26 '21 at 16:15

OneCricketeer · Answer 1 · 2021-10-26T16:21:56.950

4

That is the element of the list that will get created as part of the list-comprehension.

>>> l = [-1 for _ in range(5)]
>>> l
[-1, -1, -1, -1, -1]
>>> l[1] = 2
>>> l
[-1, 2, -1, -1, -1]

This specific example could also be written as [-1] * CAPACITY.

>>> l = [-1] * 5
>>> l
[-1, -1, -1, -1, -1]
>>> l[1] = 2
>>> l
[-1, 2, -1, -1, -1]

edited Oct 26 '21 at 16:21

answered Oct 26 '21 at 16:15

OneCricketeer

Wasn't me, but it is not the same thing in general though (similar enough for immutable objects, I'll admit) – user2390182 Oct 26 '21 at 16:18
1

@user2390182 but in this particular case it accomplishes exactly the same so I would consider it to be _the same thing_ – Matiiss Oct 26 '21 at 16:19

score 2 · Answer 2 · answered Oct 26 '21 at 16:16

2

This is a list comprehension - when expanded out it would be equivalent to:

buffer = []
for i in range(CAPACITY):
    buffer.append(-1)

answered Oct 26 '21 at 16:16

match

score 0 · Answer 3 · edited Oct 26 '21 at 16:26

0

That's a List Comprehension.

You are basically declaring a list of CAPACITY size with a for loop, all elements of that list will have a value of -1.

If you print(buffer), you will get the following output:

[-1, -1, -1, -1, -1, -1, -1, -1, -1, -1]

edited Oct 26 '21 at 16:26

BTables

answered Oct 26 '21 at 16:21

rookie

3 Answers3