Why can’t I add new attributes to an object? As in, x = object(); x.foo = 23?

  • object
>>> o = object()
>>> o.attr = 'Hello'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'object' object has no attribute 'attr'
>>> class Sub(object):
...     pass
>>> s = Sub()
>>> s.attr = 'Hello'