[Pyrex] [Cython] Proposed change to behaviour of "not None"

[Robert Bradshaw]

On Aug 22, 2008, at 12:47 AM, Kirill Smelkov wrote:

> В сообщении от Четверг 21 августа 2008  
> Greg Ewing написал(a):
>> Lisandro Dalcin wrote:
>>
>>> I know, I can (and I do) use 'Type arg is not
>>> None' in argument lists, but I never liked it.
>>
>> Speaking of that, I've been thinking for a while now
>> about making "not None" the default, and requiring
>> "or None" to specify that None is an acceptable
>> parameter value.
>>
>> Having seen a number of pieces of Pyrex code that
>> were susceptible to being crashed because "not None"
>> wasn't used where it should have been, I think
>> this would be a safer default. The change may
>> break some existing code, though.
>>
>> What do people think?
>
> I'm +1 for having "not None" the default.
>
> I was always wondering why was it the vice versa when I was  
> stydying Pyrex --
> for internal functions this was creating additional overhead and  
> additional
> inconvenience, and I'd better put "or None" explicitely where it  
> makes sence
> -- for high-level functions who interface with Python level.
>
>
> Bearing backward compatibility in mind, maybe let's create a  
> compile option to
> switch this behaviour? And we'll remove old behaviour step-by-step:
>
> o first declare there is new "not None" by default with explicit  
> switch, saying
>   it will be the default in the next release.
> o then make default "not None" default and allow users to switch  
> back with
>   cython/pyrex option, but say this old behaviour will be removed  
> in the next
>   release
> o remove old behaviour in the next release.
>
> Sounds reasonable?

I am still -1 to the idea, but keep trying to convince me :).  
Certainly I would like things to be more friendly then they are right  
now, but having two kinds of extension class types that are declared  
exactly the same way, one of which can take a None and the other  
can't, seems odd. Certainly enabling a switch to check for this is  
something I want to have, and not limited to python function  
arguments either.

- Robert