Python - How to sort multidimensional list to two-dimensional list?

Question

How i can sort multidimensional list to two-dimensional list?

Multidimensional input: [8, [6, 7, [-1], [4, [[10]]], 2], 1]

Desired two-dimension

Answer 1

You can do this by first generating a dictionary of elements at each depth (with depth as key in this dictionary and list of elements of that depth as value). The recursive function get_elements_by_depth below does this. Then all you need to do is flatten the values of that dictionary. (the function flatten_by_depth below does what you need).

from collections import defaultdict

def get_elements_by_depth(ls, cur_depth, cur_dict):
    """
        returns a dictionary with depth as key and a list of all
        elements that have that depth as value
    """
    for x in ls:
        if isinstance(x, list):
            get_elements_by_depth(x, cur_depth + 1, cur_dict)
        else:
            cur_dict[cur_depth].append(x)
    return cur_dict


def flatten_by_depth(ls):
    """
        returns a list of lists, where the list at index i 
        contains all elements of depth i
    """
    elements_by_depth = get_elements_by_depth(ls, 0, defaultdict(list))
    max_depth = max(elements_by_depth.keys())
    # Since we're using a defaultdict, we don't have to worry about
    # missing keys in elements_by_depth
    return [
        elements_by_depth[i]
        for i in xrange(max_depth + 1)
    ]

---

> flatten_by_depth([8, [6, 7, [-1], [4, [[10]]], 2], 1])
[[8, 1], [6, 7, 2], [-1, 4], [], [10]]