Split a Python list logarithmically

Question

I am trying to do the following..

I have a list of n elements. I want to split this list into 32 separate lists which contain more and more elements as we go towards the end of the original list. For example from:

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

I want to get something like this:

b = [[1],[2,3],[4,5,6,7],[8,9,10,11,12]]

I've done the following for a list containing 1024 elements:

for i in range (0, 32):
    c = a[i**2:(i+1)**2]
    b.append(c)

But I am stupidly struggling to find a reliable way to do it for other numbers like 256, 512, 2048 or for another number of lists instead of 32.

Answer 1

Use an iterator, a for loop with enumerate and itertools.islice:

import itertools
def logsplit(lst):
    iterator = iter(lst)
    for n, e in enumerate(iterator):
        yield itertools.chain([e], itertools.islice(iterator, n))

Works with any number of elements. Example:

for r in logsplit(range(50)):
    print(list(r))

Output:

[0]
[1, 2]
[3, 4, 5]
[6, 7, 8, 9]
... some more ...
[36, 37, 38, 39, 40, 41, 42, 43, 44]
[45, 46, 47, 48, 49]

In fact, this is very similar to this problem, except it's using enumerate to get variable chunk sizes.