如何从递归 function 返回列表？

Question

I'm trying to return a list from the following recursive function, where should I do it?. I think I cant manage to do it because I do not fully understand all the function steps so how can I follow each step of the recursion using the debugger? (pycharm) Thanks for the helpers!!

def parentheses_helper(open, close, word, lst):
    """ get 2 equal integers and return all the combination of balanced parantheses """
    if open == 0 and close == 0:
        lst.append(word) 
        print(lst)
    if open > close:
        return
    if open > 0:
        parentheses_helper(open - 1, close, word + '(', lst)
    if close > 0:
        parentheses_helper(open, close - 1, word + ')', lst)


def parentheses(n):
    parentheses_helper(n, n, '', [])

Answer 1

If you need to return the list from function parentheses you can create a list variable inside of it and pass to parentheses_helper and then return the variable. This will work, because you are modifying the same list inside of parentheses_helper (the list is not getting copied)

def parentheses(n):
    lst = []
    parentheses_helper(n, n, '', lst)
    return lst