Python: How do I pass a string by reference?

Question

From this link: How do I pass a variable by reference?, we know, Python will copy a string (an immutable type variable) when it is passed to a function as a parameter, but I

Answer 1

wrapping the string into a class will make it pass by reference:

    class refstr:
       "wrap string in object, so it is passed by reference rather than by value"
       def __init__(self,s=""):
          self.s=s
       def __add__(self,s):
          self.s+=s
          return self
       def __str__(self):
          return self.s

    def fn(s):
       s+=" world"

    s=refstr("hello")
    fn(s) # s gets modified because objects are passed by reference
    print(s) #returns 'hello world'