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unexpected behaviour in class variables

Gordon McMillan gmcm at hypernet.com
Tue Jun 27 16:25:41 EDT 2000 
Andrew Dalke wrote: 

>Gordon McMillan wrote:

>>An attribute found in the instance dict will never get wrapped. Only
>>stuff found in the class __dict__ (or in a base class __dict__)
>>qualifies for wrapping.
>
>
>But the documentation at http://python.org/doc/current/ref/types.html
>says (with some spacing changes to enforce better alignment)
>
>: User-defined method objects are created in two ways: when getting
>:  an attribute  of a class          that is a user-defined function
>:  object, 
>: or when getting
>:  an attributes of a class instance that is a user-defined function
>:  object. 
>
>Isn't an "instance dict" in your terminology the same as "attributes of
>a class instance" in the quoted documentation?  

Terminology sherminology!

>>> def eggs():
...  pass
...
>>> class A:
...  pass
...
>>> a = A()
>>> a.eggs = eggs
>>> type(a.eggs)
<type 'function'>
>>>

It ain't wrapped. Beat up Fred, he needs it <wink>.

>>Why the wrapping? To hide away "self" - so it's implicit to the method
>>object but explicit to the function object.
>>
>>Make sense now?
>
>
>No.  Why does it only occur for user-defined function objects added to
>the class namespace and not C-based functions or callable objects?  That
>limits how I design my code if I want the ability to change between a
>C-based implementation, a Python-based one or to a function object,
>which is exactly the problem I have.  (I replaced a call to a C
>extension library to a Python based one used for regression tests.)

I'm not really understanding.

>>> class A:
...  pass
>>> A.sin = math.sin
>>> def eggs(x):
...  print "eggs"
...
>>> A.eggs = eggs
>>> a = A()
>>> a.eggs()
eggs
>>> a.sin(0)
0.0

Functionally, the difference is the need to provide an arg to the user-
defined function that will take the value of "self". Or, perhaps, the 
inability to use one in a C extension. Maybe your original post spelled out 
some brilliantly deduced logical consequences of this apparently innocuous 
difference. If so, they slid right past me <wink>.

- Gordon
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