How to subclass str in Python

Overwriting __new__() works if you want to modify the string on construction:

class caps(str):
   def __new__(cls, content):
      return str.__new__(cls, content.upper())

But if you just want to add new methods, you don’t even have to touch the constructor:

class text(str):
   def duplicate(self):
      return text(self + self)

Note that the inherited methods, like for example upper() will still return a normal str, not text.