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

Answer 1

Here's an idea. It isn't perfect, because it doesn't work for all strings, but it might be helpful.

To set attributes of a string or any other object:

def attr(e,n,v): #will work for any object you feed it, but only that object
    class tmp(type(e)):
        def attr(self,n,v):
            setattr(self,n,v)
            return self
    return tmp(e).attr(n,v)

Here's an example:

>>> def helloWorld():
...     print("hello world!") #python 3
...
>>> a=attr("foo",'heloWorld',helloWorld)
>>> a
'foo'
>>> a.helloWorld()
hello world!
>>> "foo".helloWorld()
Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    "foo".helloWorld()
AttributeError: 'str' object has no attribute 'helloWorld'

Answer 2

You don't. Use separate dictionaries to "attach" (logically speaking) information to immutable values like strings or numbers (the string or number value as key, the information as corresponding value in the dict).