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[Python-Dev] [numpy wishlist] Interpreter support for temporary elision in third-party classes

Greg Ewing greg.ewing at canterbury.ac.nz
Fri Jun 6 04:17:20 CEST 2014 
Nathaniel Smith wrote:
> I.e., BIN_ADD could do
> 
> if (Py_REFCNT(left) == 1)
>     result = PyNumber_InPlaceAdd(left, right);
> else
>     result = PyNumber_Add(left, right)
> 
> Upside: all packages automagically benefit!
> 
> Potential downsides to consider:
> - Subtle but real and user-visible change in Python semantics.

That would be a real worry. Even if such cases were rare,
they'd be damnably difficult to debug when they did occur.

I think for safety's sake this should only be done if the
type concerned opts in somehow, perhaps by a tp_flag
indicating that the type is eligible for temporary
elision.

-- 
Greg
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