Hi Andreas,

As Hanno said, you'll still be in old-style-classes-land even in Python 2.7 unless you inherit from `object` directly.

You said:

My idea is to inject a common mixin class like
    class Foo(Bar, Mixin):
        ...
    class Mixin:
        def __getattr__(self, k)
           print repr(self), k
           return Foo.__getattr__(self, k)

Your recursion error is caused by calling `Foo.__getattr__(self, k)` from `Mixin`, but `Foo` inherits from `Mixin`. Calling a method of a subclass from the same-named method in the superclass is a recurssion.

Instead `Mixin` needs to call `Bar.__getattr__` since `Bar` is the superclass to `Foo`.

Alternatively, if you don't want to name any specific superclass inside the mixin method, (and since you can't use `super()` since you're using old-style classes), I suggest a different approach. Instead of a mixin class, use a method factory, like this:

def my__getattr__factory(SuperClass):
    def __getattr__(self, k):
        print repr(self), k
        return SuperClass.__getattr__(self, k)

Which you can then use as:

class Foo(Bar):  # <- No mixin 

    __getattr__ = my_getattr__generator(Bar)  # <- Bar, not Foo

Regards,

Leo

On 7 November 2016 at 12:29, Hanno Schlichting <hanno@hannosch.eu> wrote:
On Mon, Nov 7, 2016, at 14:01, Andreas Jung wrote:
> Python 2.7 is different because all classes are automatically new-style
> classes.
> In Python 2.7 you would have to overwrite __getattribute__() but I am on
> Python 2.3 here.

No :)

In Python 3 all classes are new-style classes. In Python 2 (including
2.7) you have to be explicit and either inherit from object (new-style)
or not (old-style).

In Python 2.7 you get:

>>> class A: pass
>>> class B(object): pass
>>> type(A)
<type 'classobj'>
>>> type(B)
<type 'type'>

In Python 3 both are of type 'type'.

And only new-style classes use '__getattribute__'. '__getattr__' is the
right approach for old-style classes in any Python 2 version, even in
Python 2.7.

Hanno
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