[Bf-python] Proposed BPyAPI Additions.

[Willian Padovani Germano]

Food for thought:

Maybe forcing users to reset the iterator (of course if it's not at its 
start anymore) before being able to add or remove itens is not a bad option.

After all, if you iterate a little, then break out of the loop and add 
or remove something, what is the state of the list? What you removed has 
already been looped over or not? Only by keeping some control and doing 
some testing the user would know.

There's useful info at the very end here: 
http://www.python.org/doc/2.2.3/whatsnew/node4.html

Here's what is written there:

"Note that you can only go forward in an iterator; there's no way to get 
the previous element, reset the iterator, or make a copy of it. An 
iterator object could provide such additional capabilities, but the 
iterator protocol only requires a next() method."

So we could add .reset() methods (e.g. scene.objects.reset()) to let 
users rewind an iterator to its beginning, for the rare cases where it 
would be needed. This would let us forbid adding/removing inside loops.

Opinions?

Campbell Barton wrote:
> Looks like its keeping a count with
> 
> mp->ma_used;
> 
> If this changes in size then it raises an error, to do this properly 
> we'll probably need to store some data in the scene, though using the 
> pyType may be weak but good enough.
> 
> Willian Padovani Germano wrote:
>> Hi, Campbell
>>
>> Python dictionaries do it, so it's a good place to start looking for 
>> ideas. I just saw the error msg here (function dictiter_iternextkey ) :
>>
>> http://svn.python.org/view/python/trunk/Objects/dictobject.c?rev=52550&view=markup 
>>
>>
>> Will spend some time on this weekend, to learn more about the 
>> possibilities.
>>
>> Campbell Barton wrote:
>>> Hey Willian,
>>> I dont think we can stop people from adding new objects while iterating.
>>>
>>> I thaught doing somthing like only allowing to add a new object when 
>>> the the pypypes  "iter" value is NULL
>>> would be ok but  it wont work if you break early.
>>>  
>>> I think the only way it can be done is to use a refcounter on the 
>>> scene that lets python know how many scn.objects  there are iterating 
>>> (can increment on getIter), and only if its 0, let the user add objects.
>>>
>>> All up I dont think its the biggest of our problems, but interested 
>>> to see if theres another way to do this.
>>
>> It's important but probably not a show-stopper. If we can't find a 
>> good way now, it can be done later, as long as the docs clearly tell 
>> users not to add/remove objects inside loops.

-- 
Willian