downcasting problem

[Tim Chase]

On 10/25/2010 12:56 PM, John Nagle wrote:
> On 10/25/2010 7:38 AM, Tim Chase wrote:
>> While a dirty hack for which I'd tend to smack anybody who used it...you
>> *can* assign to instance.__class__
>
>      That's an implementation detail of CPython.  May not work in
> IronPython, Unladen Swallow, PyPy, or Shed Skin.

Curious by your claim, could you confirm this someplace in the 
docs?  From my reading of [1]'s "If x is an instance of a 
new-style class, then type(x) is typically the same as 
x.__class__ (although this is not guaranteed - a new-style class 
instance is permitted to override the value returned for 
x.__class__)" is that this can be overridden (the definition of 
"overridden" however may mean different things to different 
people)  and [2] refers to "__class__ assignment works only if 
both classes have the same __slots__" (that seems pretty clear 
that __class__ assignment is permissible)

-tkc


[1]
http://docs.python.org/reference/datamodel.html#new-style-and-classic-classes

[2]
http://docs.python.org/reference/datamodel.html#__slots__