[nomel]

I didn't realize this. I thought things like int's were special. I just tried

  x = 5
  dir(x)

Output:

  ['__abs__', '__add__', '__and__', '__bool__', ...

[eesmith]

Some Python objects are open for modification, and some are closed. Closed objects don't support this sort of monkey-patching.

Integers, strings, and other class objects defined in C are closed for modification.

  >>> x = 5
  >>> x.__add__ = lambda x, y: x*y
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  AttributeError: 'int' object attribute '__add__' is read-only

In that sense they are "special" (or class objects defined in Python are special).

But that doesn't make a language with closed classes non-OO.