Convert tree string to dictionary

parse_tree.py

""" Function to convert a tree in string format to a dictionary.
There is no error handling.
It doesn't allow a level to be skipped.
"""
def tree_child(acc, path, element):
    node = element.lstrip()
    current = None
    for p in path:
        if current:
            current = current[p]
        else:
            current = acc[p]
    current[node] = dict()
    return node

def tree_sibling(acc, path, element):
    return tree_child(acc, path[:-1], element)

def _parse_tree(acc, path, indent, tree_ls):
    """ Recursive function parsing a list.
    
    Args:
        acc(dictionary): accumulator dictionary used both as in-out
        path(list): current node
        indent(str): indentation value used to identify depth of tree
        tree_ls(list): list of lines indented following indent
        
    Returns:
        dictionary: dictionary corresponding to tree_ls provided
    """
    #print(acc, path)
    if tree_ls:
        line = tree_ls[0].rstrip()
        if not line:
            return _parse_tree(acc, path, indent, tree_ls[1:])
        if not path:
            node = line.lstrip()
            acc[node] = dict()
            return _parse_tree(acc, [node], indent, tree_ls[1:])
        next_indent = indent * len(path)
        current_indent = next_indent[:-len(indent)]
        if len(line) > len(next_indent) and line[:len(next_indent)]==next_indent:
            node = tree_child(acc, path, line[len(next_indent):])
            return _parse_tree(acc, path+[node], indent, tree_ls[1:])
        if len(line) > len(current_indent) and line[:len(current_indent)]==current_indent:
            node = tree_sibling(acc, path, line[len(current_indent):])
            return _parse_tree(acc, path[:-1]+[node], indent, tree_ls[1:])
        # back up the tree and parse recursively
        return _parse_tree(acc, path[:-1], indent, tree_ls)
    # end of recursion
    return acc

def parse_tree(tree_st, indent):
    res = dict()
    path = []
    val_ls = tree_st.split('\n')
    return _parse_tree(res, path, indent, val_ls)

if __name__=="__main__":
    tree = """
one
    one
        one
        two
    two
        one
    three
        one
        two
        three
"""
    print(parse_tree(tree, "    "))