How do I add my own custom attributes to existing built-in Python types? Like a string? [duplicate]

Answer 1

Ruby way:

"1".to_i
"1".to_roman 

Python way:

int("1")
Roman("1") # or 
Roman.fromstring("1") 

Where Roman will work on a fixed list of built-in types or anything with a __int__ method.

It is an implementation limitation of CPython that you can't set attributes of built-in/extension types. It is accompanied by cultural preference to avoid monkey-patching in favor of stand-alone functions, custom classes that have as an attribute desired object (or even subclassing in rare cases).