Detect target name in descriptor __set__ method

[Jon Clements]

On 22 July, 06:02, "Gabriel Genellina" <gagsl-... at yahoo.com.ar> wrote:
> I have a class attribute 'foo' which is a data descriptor. I create an  
> instance of such class. When I say instance.foo = value, the descriptor  
> __set__ method is called. Is there any way to obtain the name being  
> assigned to? ('foo' in this example). That is, I want to know the target  
> name for the assignment that triggered the __set__ method call.
>
> class descriptor(object):
>    def __get__(self, instance, owner):
>      print 'descriptor.__get__ self=%r instance=%r owner=%r' % (
>        self, instance, owner)
>      return self
>
>    def __set__(self, instance, value):
>      # I want to know the *name* this value is being assigned to
>      print 'descriptor.__set__ self=%r instance=%r value=%r' % (
>        self, instance, value)
>
>    def __delete__(self, instance):
>      print 'descriptor.__delete__ self=%r instance=%r' % (
>        self, instance)
>
> class X(object):
>    foo = descriptor()
>
> x = X()
> x.foo = "value"
>
> I can obtain the name descriptor() was assigned to at the time the X class  
> was defined, using a custom metaclass:
>
> class Meta(type):
>    def __new__(meta, name, bases, dict):
>      for key,value in dict.iteritems():
>        if isinstance(value, descriptor):
>          value.name = key
>      return type.__new__(meta, name, bases, dict)
>
> class Y(object):
>    __metaclass__ = Meta
>    foo = descriptor()
>
> y = Y()
> print y.foo.name # prints 'foo'
>
> This is good enough for me (assuming no one modifies the class after  
> defining it, no two names refer to the same descriptor, no two classes  
> share the same descriptor instance...). But I would like to use a more  
> direct/robust approach, if available.
>
> Any ideas?
>
> --
> Gabriel Genellina

>>> class Test:
	def __setattr__(self, what, value):
		print what, value


>>> t = Test()
>>> t.foo = 'x'
foo x

Is that what you're after?

Jon.