How to remove something from a list with recursion? Python

Question

I have this exercise:

You have a tree graph as input, and you need to remove its leaves. So you need to remove the empty lists from a list of lists.

For example

Answer 1

The solution:

def tree_cut(tree):
    return [tree_cut(x) for x in tree if x]

uses a list comprehension to iterate, filter and transform nodes in the tree.

Can be written also in terms of map() and filter():

def tree_cut(tree):
    return list(map(tree_cut, filter(None, tree)))

The if x part tests if the list is not empty.

>>> tree = [[[[], []], [[], []]], [[], [], []]]
>>> tree_cut(tree)
[[[], []], []]