Question

I have to use a recursive function in python, code below is a simplified model.
I want to preserve result list and dict dictionary not generate a new list or dictionary while in the recursive, and return it after recursive, how to solve it?

def test(length):
    result = []
    dict = {}
    if length == 10:
        return result, dict
    else:
        result.append(length)
        dict[length] = length + 1
        test(length + 1)

x, y = test(0)
print x, y

Answer 1

Use a helper function that performs the recursion, and the main function to call the helper with the initial defaults.

def test(length):
    result = []
    dict = {}
    _test(length, result, dict)
    return result, dict

def _test(length, result, dict):
    if length == 10:
        return
    else:
        result.append(length)
        dict[length] = length + 1
        _test(length + 1, result, dict)

x, y = test(0)
print x, y