trying to convert string of letters and square brackets into a list of letters and lists

I’m super new to coding and solving an assignment. The problem at hand is to convert an input string of letters and square brackets into a list of letters and lists. For example:the string ‘[abc]’ should return [‘a’,‘b’,‘c’]. I have the code running for a few test cases but it fails for the following string: ‘[a[b[c]]]’ which should return [‘a’,[‘b’,[‘c’]]], but instead my code returns [ ‘a’, [ ‘b’, [ ‘c’ ] ], [ ‘c’ ] ]. Can someone please tell me what I’m missing in my logic. Please help.

Here’s my logic so far that I’ve been able to research.

def str2list(s):
    out = []
    for x in s.split('['):
        if ']' in x[:-1]:
            x1 = x.split(']')
            x1 = [list(x1[0])]+list(x1[1])
        elif x[-1:] == ']':
             x1 = list(x.strip(']'))
        else:
            x1 = list(x)
        out.extend(x1)
    return out

>Solution :

For an arbitrary nests of brackets, it’s better to use a recursive function:

def str2list(s):
    def inner(item):
        while True:
            next_item = next(item)
            if next_item == '[':
                yield [x for x in inner(item)]
            elif next_item == ']':
                return
            else:
                yield next_item
    return list(next(inner(iter(s))))

str2list('[a[b[c]]]')

Output:

['a', ['b', ['c']]]