How to customize getattr(obj, prop) function ?
Richard Copeland
rick446 at NOSPAM.usa.net
Wed May 17 12:58:04 EDT 2006
Try this:
class Class:
a='aa'
b='bb'
def __getattr__(self, ppt):
return 'custom computed result'
__getattr__ is only called when "normal" attribute lookup fails, so
there's no need for the "hasattr" test.
Also, I believe that __getattribute__ only applies to new-style classes
(classes derived from "object"), and it will override *all* attribute
accesses, anyway (meaning you'd have infinite recursion if you used it
since you look up "self.ppt")
Pierre wrote:
> Hi,
>
> Sorry in advance, english is not my main language :/
>
> I'd like to customize the result obtained by getattr on an object : if
> the object has the requested property then return it BUT if the object
> doesn't has actually this property return something else.
>
> In my case, I can't use getattr(object, property, default_value).
>
> I tried to write a class with a __getattr__ method and even a
> __getattribute__ method but this doesn't do what I want....
>
> Maybe I didn't correctly understand this :
> http://docs.python.org/ref/attribute-access.html
>
> Here is a piece of my code :
> =====================================
> class myclass:
> """docstring"""
>
> a = 'aa'
> b = 'bb'
>
> def __getattr___(self, ppt):
> """getattr"""
> if hasattr(self, ppt):
> return self.ppt
> else:
> return "my custom computed result"
>
> def __getattribute__(self, ppt):
> """getattribute"""
> if hasattr(self, ppt):
> return self.ppt
> else:
> return "my custom computed result"
>
> if __name__ == "__main__":
>
> d = myclass()
> p1 = getattr(d, "a")
> print p1
> p2 = getattr(d, "b")
> print p2
> p3 = getattr(d, "c")
> print p3
> ================================
>
> I get an AttributeError when accessing to the property named "c".
>
> Any explanation/solution to my problem ?
>
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