How do I override __getattr__ in Python without breaking the default behavior?

Question

I want to override the __getattr__ method on a class to do something fancy but I don\'t want to break the default behavior.

What\'s the correct way to d

Answer 1

class A(object):
    def __init__(self):
        self.a = 42

    def __getattr__(self, attr):
        if attr in ["b", "c"]:
            return 42
        raise AttributeError("%r object has no attribute %r" %
                             (self.__class__.__name__, attr))

---

>>> a = A()
>>> a.a
42
>>> a.b
42
>>> a.missing
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 8, in __getattr__
AttributeError: 'A' object has no attribute 'missing'
>>> hasattr(a, "b")
True
>>> hasattr(a, "missing")
False