string - Extending builtin classes in python

Question

How can I extend a builtin class in python? I would like to add a method to the str class.
I've done some searching but all I'm finding is older posts, I'm hoping someone knows of something newer.

Answer 1

Just subclass the type

>>> class X(str):
...     def my_method(self):
...         return int(self)
...
>>> s = X("Hi Mom")
>>> s.lower()
'hi mom'
>>> s.my_method()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in my_method
ValueError: invalid literal for int() with base 10: 'Hi Mom'

>>> z = X("271828")
>>> z.lower()
'271828'
>>> z.my_method()
271828