[Bf-python] [Bf-blender-cvs] SVN commit: /data/svn/bf-blender [11293] branches/pyapi_devel/source/ blender/python/api2_2x: * Added Constants to Mesh

[Ken Hughes]

Campbell Barton wrote:
> Ken Hughes wrote:
>   
>> Campbell Barton wrote:
>>     
>>> Revision: 11293
>>>           http://projects.blender.org/plugins/scmsvn/viewcvs.php?view=rev&root=bf-blender&revision=11293
>>> Author:   campbellbarton
>>> Date:     2007-07-16 23:20:52 +0200 (Mon, 16 Jul 2007)
>>>
>>> Log Message:
>>> -----------
>>> * added utility functions for new constants Const_FromPyObject to make getting the const from a PyObject easier.
>>>  (also changed a few things you may want to look Ken)
>>>   
>>>       
>> May want to discuss this further before we make a lot of changes.  One 
>> thing which came up during the discussion
>> about constants was being able to use strings instead of actual constant 
>> objects:
>>
>> ob.drawType = "BOUNDBOX"
>>
>> Turns out this was not hard to implement so I wrote an API function 
>> PyConst_Lookup() which searched for a match and
>> returned the constant's value.  But since we didn't actually agree to 
>> support this in the API, maybe we should decide whether
>> we want this or not.  Again, from a coding standpoint it's not a big 
>> issue, it's just a "standards issue".
>>
>> Ken
>>
>> (PS: description of implementation:
>> http://wiki.blender.org/index.php/BlenderDev/Bitfields#Use_of_Strings_in_Place_of_Constants 
>> )
>>     
> As long as all blenders functions use Const_FromPyObject - we can 
> keep/remove string support without touching every file that uses constants.
>
>   
Good point.

> Its nice how you can set a constant without all the prefix's of constants
>   
My tests showed that the most efficient way (i.e., fastest scripts)  to 
use constants was to assign the const to a local variable:

cnst = Object.DrawTypes.BOUNDBOX
for o in scn.active.objects:
    o.drawType = cnst


So if typing is a pain, it's actually best to put the constants into 
short variable name and use that.

> but bad how there is 2 ways to set a constant and the string isnt 
> associated with anything also a teeny bit bad how it does a lookup on 
> the constant tho if you compare with all the lookups going on in pythons 
> internals its no big deal.
>   

Yeah, the main downside is the lookup, which can be slow if there should 
be a long list of constants.  That could be mitigated by requiring that 
constants be stored in alphabetical order, but the overhead for 
something like a binary search would be significant for short lists.


> - Cam
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