Static variable vs Class variable

[Marc 'BlackJack' Rintsch]

On Wed, 17 Oct 2007 13:41:06 +0200, Hrvoje Niksic wrote:

> Duncan Booth <duncan.booth at invalid.invalid> writes:
> 
>> Hrvoje Niksic <hniksic at xemacs.org> wrote:
>>
>>> I've recently been bitten by [rebinding the var to what __iadd__
>>> returns], and I don't understand the reasoning behind __iadd__'s
>>> design.  I mean, what is the point of an *in-place* add operation
>>> (and others) if it doesn't always work in-place?
>>> 
>> A very common use case is using it to increment a number:
> 
> I'm aware of that; but remember that there's still __add__.  It would
> be sufficient for numbers not to implement __iadd__.  And, in fact,
> they already don't:
> 
>>>> 1 .__add__(1)
> 2
>>>> 1 .__iadd__(1)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> AttributeError: 'int' object has no attribute '__iadd__'
> 
> The current implementation of += uses __add__ for addition and
> __iadd__ for addition that may or may not be in-place.  I'd like to
> know the rationale for that design.

Simply not to introduce special cases I guess.  If you write ``x.a += b``
then `x.a` will be rebound whether an `a.__iadd__()` exists or not. 
Otherwise one would get interesting subtle differences with properties for
example.  If `x.a` is a property that checks if the value satisfies some
constraints ``x.a += b`` would trigger the set method only if there is no
`__iadd__()` involved if there's no rebinding.

Ciao,
	Marc 'BlackJack' Rintsch