Question

I’m trying to create a class which must be superclass of others, tracing their attribute requests. I thought of using “getattribute” which gets all attribute requests, but it generates recursion:

class Mixin(object):
 def __getattribute__ (self, attr):
  print self, "getting", attr
         return self.__dict__[attr]

I know why I get recursion: it’s for the self.dict call which recalls getattribute recursively. I’ve tryied to change last line in "return object.__getattribute__(self,attr)" like suggested in other posts but recursion is recalled.

Answer 1

Try this:

class Mixin(object):
    def __getattribute__ (self, attr):
        print self, "getting", attr
        return object.__getattribute__(self, attr)

If you are still getting recursion problems, it is caused by code you haven’t shown us

>>> class Mixin(object):
...     def __getattribute__ (self, attr):
...         print self, "getting", attr
...         return object.__getattribute__(self, attr)
...
>>> Mixin().__str__
<__main__.Mixin object at 0x00B47870> getting __str__
<method-wrapper '__str__' of Mixin object at 0x00B47870>
>>> Mixin().foobar
<__main__.Mixin object at 0x00B47670> getting foobar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 4, in __getattribute__
AttributeError: 'Mixin' object has no attribute 'foobar'
>>>

And here is the result when combined with Bob’s Mylist

>>> class Mylist(Mixin):
...     def __init__ (self, lista):
...         if not type (lista) == type (""):
...             self.value = lista[:]
...     def __add__ (self,some):
...         return self.value + some
...     def __getitem__ (self,item):
...         return self.value[item]
...     def __getslice__ (self, beg, end):
...         return self.value[beg:end]
...
>>> a=Mylist([1,2])
>>> a.value
<__main__.Mylist object at 0x00B47A90> getting value
[1, 2]