how do you split list into x lists without using the elements on the inside?

Question

Working on an assignment, which in one of the parts requires me to split the list into "x" chunks of lists but I don't necessarily want to use the elements inside the list to do so as I have seen many examples that do this. For example, given the list [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15], I want to split this list into 3 even parts ([[1,2,3,4,5],[6,7,8,9,10],[11,12,14,15]]).

Most of the examples that I have seen on here tend to divide the whole list by "x" rather than making "x" groups of it which end up giving me a list like [[1,2,3],[4,5,6],[7,8,9],[10,11,12],[13,14,15]].

EDIT:

I've figured out how to get the desired output in the first part of this question that I was looking for but upon looking at my assignment further, I realized the lists that need to be made have to go up in increments of lst rather than having to put a value in which would generate a list in that range. For example if I want to print out a grouped list like [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15]] I don't want to have have to set lst to lst = list(range(1,lst+1)) and then when I'm assigning values to my function, I want to be able to put 5 in place of 15 to get the same result.

def test(num, lst, start = 1):
    lst = list(range(start,lst+1))
    avg = len(lst) / float(num)
    out = []
    last = 0.0

    while last < len(lst):
        out.append(lst[int(last):int(last + avg)])
        last += avg

    return out

print (test(3,15))

Does this answer your question? [Splitting a list into N parts of approximately equal length](https://stackoverflow.com/questions/2130016/splitting-a-list-into-n-parts-of-approximately-equal-length) — ggorlen, Nov 25 '19 at 20:01
Or possibly this: https://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-evenly-sized-chunks — gen_Eric, Nov 25 '19 at 20:01
Simple arithmetic. If you want `x` groups from a list with `n` items, then you just need to calculate `n / x`, and then you can divide the whole list by that result. Given 5 groups of a list with 20 elements, you need to split every 4 items. — DetectivePikachu, Nov 25 '19 at 20:02
Could you clarify these parts? *"without using the elements on the inside"* ... *"I don't necessarily want to use the elements inside the list to do so"*. — wjandrea, Nov 25 '19 at 20:57
If the length of the list isn't a multiple of `rows`, where should the remainder go? — wjandrea, Nov 25 '19 at 21:00
BTW that code output doesn't include 15. It looks like you just forgot to add 1: `list(range(1, lst+1))` — wjandrea, Nov 25 '19 at 21:03
@wjandrea I realized the lists that need to be made have to go up in increments of "lst" rather than having to put a value in which would generate a list in that range. Any suggestions would be appreciated — snk, Nov 25 '19 at 21:24

score 0 · Answer 1 · answered Nov 25 '19 at 21:36

Most of the examples that I have seen on here tend to divide the whole list by "x" rather than making "x" groups of it which end up giving me a list like [[1,2,3],[4,5,6],[7,8,9],[10,11,12],[13,14,15]].

In your example, a list of 15 elements divided into chunks of 3 makes 5 groups. It's too bad you didn't want five groups instead of three, you would have been done already!

If only there was a way to divide 15 elements with different sized chunks such that you would have 3 groups =)

Hint:

3 x 5 = 15
5 x 3 = 15

tl;dr: If you believe that dividing a list into chunks of size "x" is different than making "y" groups, then you should take a minute to reconsider.

how do you split list into x lists without using the elements on the inside?

1 Answers1