Getting two different values from a recursive function?

Question

I am trying to create a function in python that splits a string in to two strings, where the first one have all the lower case letters + some other special characters and the second one having all the upper case letters + special characters.

The point is to be able to type:

>>> first_message,second_message=string_split("SomEChaRacTers")
>>> print(first_message, second_message)

to get the result printed.

This is what i have right now:

def string_split(string):
    first_message_signs = "_."
    second_message_signs = " |"
    one = ""
    two = ""
    if len(string) == 0:
        return string
    
    if string[0].islower() or string[0] in first_message_signs:
        one += string[0] + string_split(string[1:])
        return one
    
    elif string[0].isupper() or string[0] in second_message_signs:
        two += string[0] + string_split(string[1:])
        return two
    else:
        return string_split(string[1:])

I am getting this error when making the first call in the prompt: Traceback (most recent call last): File "", line 1, in ValueError: too many values to unpack (expected 2)

When i try with only message_one i get all the characters in one string.

What should i do?

Answer 1

Your first line

first_message,second_message=string_split("SomEChaRacTers")

expects string_split to return two values. However, your function only ever returns one.

What you want is

def string_split(string):
    first_message_signs = "_."
    second_message_signs = " |"
    one = ""
    two = ""
    if len(string) == 0:
        return one, two
    
    if string[0].islower() or string[0] in first_message_signs:
        one += string[0]
    elif string[0].isupper() or string[0] in second_message_signs:
        two += string[0]

    ret1, ret2 = string_split(string[1:])
    one += ret1
    two += ret2

    return one, two

On a side note, there's no compelling reason for string_split to be recursive. Try this:

def string_split(string):
    first_message_signs = "_."
    second_message_signs = " |"

    one = ''.join(c for c in string if c.islower() or c in first_message_signs)
    two = ''.join(c for c in string if c.isupper() or c in second_message_signs)

    return one, two