instance.attribute lookup

[Ethan Furman]

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

 

[Steven D'Aprano]

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.

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

I'm thinking I don't even understand what step 1 means.

What's a Python-provided attribute, and how is it different from other
attributes?

 

[Ethan Furman]

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.

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

I'm thinking I don't even understand what step 1 means.

What's a Python-provided attribute, and how is it different from other
attributes?

Well, if /you/ don't understand it I feel a lot better about not
understanding it either!

Glad to know I'm not missing something (besides ESP, a crystal ball, and
a mind-reader!)

~Ethan~

 

[Mark Lawrence]

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

I'm thinking I don't even understand what step 1 means.

What's a Python-provided attribute, and how is it different from other
attributes?

Well, if /you/ don't understand it I feel a lot better about not
understanding it either!

Glad to know I'm not missing something (besides ESP, a crystal ball, and
a mind-reader!)

~Ethan~

My probably highly uneducated guess is that "Python-provided attribute"
refers to double underscore names. YMMV by several trillion light years