[Bf-python] some suggestions for bpy

[Campbell Barton]

Hi Theo, thanks for the review. Can I forward this to the python mailing
list?

A chance for more people to discuss can be good.

My comments are inline.

On Wed, 2007-10-17 at 12:02 +0200, Theo de Ridder wrote:
> Inspired by many discussions during the Blender conference I thougth  
> a little
> about what would make bpy a lot closer to what I prefer without  
> changing its
> basic concepts. So here some first ideas.
> 
> - bpy.data
> 	'data' is a word that is very overloaded in Blender, I would suggest  
> to use 'blocks' instead,
> 	its a plural, close to LibBlockSeq, and much less confusing than  
> 'data'.

This sounds good, I never really liked any of the terms we looked at,
datablock is more correct, but I prefer to keep the names short.

> - bpy.data.scenes, bpy.data.meshes, ...
> 	all deliver the same type (reflecting C), but why not have subtypes  
> of LibBlockSeq ?
Agree, this is good. When I wrote this I didnt know how to write
subtypes, youll see in the new api, all data with an ID is a subtype. so
variables like .name, .users .lib, .tag and .properties are all in the
base type.

> 
> - bpy.data.<seqname>.new(...)
> 	'add' would be less confusing than 'new' (or else 'addnew')

Disagree, add() indicates that the arguments passed 'are' the data being
added.

say for a python set type.
someset.add(sometuple) # this is correct because sometuple is being
added to the set.

.addnew() is correct, but Im not fond of the name.
.new() is short and it indicates that new data is being created, the
arguments are just parameters.

> - bpy.data.<seqname>[<str>]
> 	why not accept also a regular expr as index selecting a subsequence?
> 	which combined with previous subtype remark enables: bpy.blocks[<re>]
> 	(grouping different types by common parts in names)

Not sure, sounds interesting but I have never seen this used in another
API.
At a guess, could this do something like return all objects and groups
based on pattern matching?
Can you give an example of how it would be useful?

> - bpy.blocks.<seqname>.attrs[<attrname>]
> 	creates an efficient iterator for a specific attribute like 'loc'

This is very cool! however is this was added it might be nice to somehow
allow the scripter to define their own sets of data. maybe allow this
sequence type - un-attached to blenders linked lists. though we need to
be careful with pointers of course!

So agree, but operating on all data is not ideal either,  need a nice
way to have your own sequence/lists.

> 
> - bpy.blocks.<seqname>.attrs[<attrname>] = <value_sequence>
> 	efficient assignment of a certain attribute of each element in a seq  
> in 1 assigment
> 	(without looping in Python)


same as above. efficient grouping is great, just need a way to define
what is being operated on.

Note that we already have this in some areas..

you can do bpy.data.meshes.tag = True
and mesh.tag = True

object.sel = False
scene.objects.selected = [] # another example, could also accept
true/false too.


Since the sequence's dont have many attributes themselves, do you think
having the same attributes on the sequence is acceptable? (as shown
above)

That IS a bit messy though, so having every attribute accessed as you
say is good. just a bit more text for the scripter to type.

Many people forget that blender can make heavy use of multiple scenes,
once you start doing this, operating on bpy.data.objects is not so nice,
and even risks messing up data in other scenes, especially bad because
you often dont notice and save over your file with bad data. (This has
happened to me before)

so this attribute access would need to work for scene.objects too, and
group.objects would be nice also.

> I will experiment with wrapping these last 2 techniques in numpy, if  
> that works
> indeed efficiently than what I did now specifically with keyblocks  
> can be applied very generic
> for any collection.
> 
> Theo
> 
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