[Bf-python] Re: Request for adding a proposed new feature

[Ken Hughes]

Eric-Olivier Le Bigot wrote:
>   Hello everybody,
> 
>   How about using the Python no-brainer
> 
>     del obj
> 
> In fact, the intended behavior is to completely get rid of the object, 
> which is what is meant by "del".  The implementation of the __del__ 
> method would imply unlinking the object from any scene it is in.

I just double-checked before replying and this did what I though it 
would do:  "del obj" calls the object deallocation function 
Object_dealloc(), so there's no way to distinguish this from the normal 
object deallocation.

>   Furthermore, in
> 
>     scn.objects.remove([ob1, ob2...],delete=True)
> 
> what happens when the object is linked to many scenes?  I guess that 
> "scn" is a specific scene: the semantics of the above call is not 
> totally transparent, as a method on a single scene would destroy objects 
> in many scenes.

That's the case: scn.objects.remove() only handles the object within the 
context of this scene, and "delete=True" further specifies that if this 
was the last user of the object, completely delete the object.

If we need a method to delete an object from all scenes, that's 
something which probably should be added as a function, like 
Object.Delete().

Two other comments though:
(1) did we decide during the Sunday morning meeting a few weeks ago to 
use objects.remove() instead of .unlink()?  Or did Cam or I misquote the 
method earlier?
(2) I was looking into adding the "delete=True" support this morning 
when I remembered that it doesn't matter whether the objects are created 
by Object.New(), Object.Get() or scn.objects: since they're all 
BPy_Objects all objects get their user count incremented, so the nice 
new scene.objects API isn't going to fix that problem :-(

Ken

>   Please forgive me if the remarks above are naive or misguided: I'm new 
> to Blender and its Python module :)
> 
>   EOL
> 
> On Tue, 19 Dec 2006, Ken Hughes wrote:
> 
>> Campbell Barton wrote:
>>> How about we allow
>>>
>>> scn.objects = []
>>>
>>> Other possibilities are...
>>>
>>> scn.objects.remove([ob1, ob2...])
>>
>> I was thinking more about making complete deletion optional per object 
>> (or group of objects):
>>
>> #remove from scene, but don't delete when user count = 0
>> scn.objects.remove([ob1, ob2...])
>> #remove from scene, delete objects with user count = 0
>> scn.objects.remove([ob1, ob2...],delete=True)
>>
>> Maybe some scripters don't want to delete the object when they become 
>> zero (the current behavior).
>>
>> The reason I suggest adding it here and not in the Object module is 
>> the nastiness we added earlier where Object.Get() and Object.New() 
>> become users of the object.  It makes deleting the object a bit of a 
>> pain when you're also a user of it.  Can fakeUser take care of that 
>> old problem now so we don't have to mess with the user count?
>>
>>> Ken Hughes wrote:
>>>> The more the merrier... so I'm cc'ing Campbell:
>>>>
>>>> This is not hard to do, but should be done in a way which doesn't 
>>>> break backward compatibility.  I think this would be something to 
>>>> consider adding to the Scene.objects sequence type, maybe with an 
>>>> optional parameter to specify completely deleting the object.
>>>>
>>>> Might be a good idea to run this through the BPy mailing list since 
>>>> we should decide ASAP before the CVS freeze.
>>>>
>>>> Ken
>>>>
>>>> Tom M wrote:
>>>>> I think this is already doable, ccing ken because i think he added it.
>>>>>
>>>>> (...)
>>>>>
>>>>> LetterRip
>>>>>
>>>>> On 12/19/06, Eric-Olivier Le Bigot 
>>>>> <Eric.Le.Bigot at spectro.jussieu.fr> wrote:
>>>>>> Hello,
>>>>>>
>>>>>> I'd like to propose a feature for the Python API, and I would like 
>>>>>> to know
>>>>>> whether I can get modification rights on
>>>>>> http://mediawiki.blender.org/index.php/BlenderDev/DesignIssues in 
>>>>>> order to
>>>>>> add this feature to the list.
>>>>>>
>>>>>> In fact, as far as I understand, it is not currently possible to 
>>>>>> remove an
>>>>>> object in the same way as the deletion in the 3D window does.  
>>>>>> Many people on
>>>>>> Blender Artists have run into this problem, which is particularily 
>>>>>> acute for
>>>>>> me.
>>>>>>
>>>>>> I need to run a script that create 1000s of objects after emptying 
>>>>>> the
>>>>>> current scene; the problem is that this "emptying" is only done 
>>>>>> with unlinks:
>>>>>> even though the first run is very fast, subsequent runs are 
>>>>>> extremely slow
>>>>>> (maybe because of memory issues, or because the objects created 
>>>>>> during the
>>>>>> second run have names that clash with those of the unlinked 
>>>>>> objects?).
>>>>>>
>>>>>> It would be very useful for me if the deletion command "x" of the 
>>>>>> 3D window
>>>>>> could have a Blender Python equivalent (as the "x" command does 
>>>>>> remove the
>>>>>> objects from memory, if this is possible).
>>>>>>
>>>>>> Best wishes,
>>>>>>
>>>>>> EOL
>>>>>>
>>>>>> -- 
>>>>>> Dr Eric-Olivier LE BIGOT (EOL)                 CNRS Associate 
>>>>>> Researcher
>>>>>> ~~~o~o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~o~o~~~ 
>>>>>> Kastler Brossel Laboratory (LKB)
>>>>>> Université P. & M. Curie and Ecole Normale Supérieure, Case 74
>>>>>> 4 place Jussieu              75252 Paris CEDEX 05                 
>>>>>> France
>>>>>> ~~~o~o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~o~o~~~ 
>>>>>> office  : (+33) 1 44 27 73 67                   fax: (+33) 1 44 27 
>>>>>> 38 45
>>>>>> ECR room: (+33) 1 44 27 47 12            x-ray room: (+33) 1 44 27 
>>>>>> 63 00
>>>>>> home: (+33) 1 73 74 61 87  
>>>>>> http://dirac.spectro.jussieu.fr/index_en.html
>>