Can set any property of Python object

Question

For example, this code is Python:

a = object()
a.b = 3

throws AttributeError: \'object\' object has no attribute \'b\'

Answer 1

Python generally allows you to set any attribute on any object. This is a special case where the object class acts differently. There are also some modules implemented in C that act similarly.

If you want your object to behave like this, you can define a __setattr__(self, name, value) method that explicitly does a raise AttributeError() if you try to set a member that's not on the "approved list" (see http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/389916)