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Groups > comp.lang.python > #30827

instance.attribute lookup

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There is a StackOverflow question [1] that points to this on-line book 
[2] which has a five-step sequence for looking up attributes:

 > When retrieving an attribute from an object (print
 > objectname.attrname) Python follows these steps:
 >
 > 1. If attrname is a special (i.e. Python-provided) attribute for
 > objectname, return it.
 >
 > 2. Check objectname.__class__.__dict__ for attrname. If it exists and
 > is a data-descriptor, return the descriptor result. Search all bases
 > of objectname.__class__ for the same case.
 >
 > 3. Check objectname.__dict__ for attrname, and return if found. If
 > objectname is a class, search its bases too. If it is a class and a
 > descriptor exists in it or its bases, return the descriptor result.
 >
 > 4. Check objectname.__class__.__dict__ for attrname. If it exists and
 > is a non-data descriptor, return the descriptor result. If it exists,
 > and is not a descriptor, just return it. If it exists and is a data
 > descriptor, we shouldn't be here because we would have returned at
 > point 2. Search all bases of objectname.__class__ for same case.
 >
 > 5. Raise AttributeError

I'm thinking step 1 is flat-out wrong and doesn't exist.  Does anybody 
know otherwise?

~Ethan~

[1]
http://stackoverflow.com/q/10536539/208880

[2]
http://www.cafepy.com/article/python_attributes_and_methods/ch01s05.html

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instance.attribute lookup Ethan Furman <ethan@stoneleaf.us> - 2012-10-05 10:39 -0700
  Re: instance.attribute lookup Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-05 23:00 +0000
    Re: instance.attribute lookup Ethan Furman <ethan@stoneleaf.us> - 2012-10-05 16:12 -0700
    Re: instance.attribute lookup Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-06 00:32 +0100

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