[Bf-python] Ipo/IpoCurve API revisited

[Ken Hughes]

Ken Hughes wrote:
> Toni Alatalo wrote:
> 
>> On Saturday 11 March 2006 23:33, Ken Hughes wrote:
>>
>>> the direction that the API rewrite was taking (which apparently for now
>>
>>
>> we talked about this a bit with Ken and Jestie on irc - revisiting 
>> many issues that were talked on this list last year etc. i try to 
>> summarize here a bit.
>>
>>>> (read-only).  Makes it possible to do "ipo['LocX']" or "ipo[Ipo.LocX]";
>>>> something like ipocurve[framenum] to do current .evaluate(framenum) 
>>>> might
>>
>>
>> again i remembered that someone said that obipo.loc_x would be nicer 
>> than obipo.['LocX'] for that and i think i agree.. (classes in py are 
>> just syntactic sugar on dicts anyway, like the perl ppl say :)
> 
> After thinking about this, I don't know if this will work with tp_getset 
> (or at least not easily).  I'm trying to interpret PEP 252 but it seems 
> that "__slots__" might allow per-instance attributes, if only I can 
> figure out how to implement them.

Woo-hoo.  Kind of.

I figured out a way to add instance-dependent attributes like ipo.LocX 
using the ob_type->tp_getattro entry.  I haven't tested 
ob_type->tp_setattro yet but assume a similar trick will work.  The 
downside is that making things like "dir(ipo)" or "ipo.__dict__" show 
the attributes (much less "help(ipo)"; haven't even figured that out 
yet) is that a new temporary dict needs to be constructed with the 
additional PyDescr_NewGetSet() objects.

My personal feeling is that this is much more of a kludge than 
"ipo['LocX']".  The implementation for that seems very clean.  The 
key/iterator similarity particularly, in case you want to do something 
to all curves (for example, delete all of them):

for x in ipo:
     ipo[x] = None

and

ipo['LocX'] = None

I assume that if we do go with attributes instead of dictionaries that 
the iterator would just return an IpoCurve:

for icu in ipo:
     icu = None

Anyway, maybe this can be discussed in the next Sunday meeting, assuming 
all the Orange people have sobered up by then :-)

Ken