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[Python-Dev] Inplace operations for PyLong objects

Greg Ewing greg.ewing at canterbury.ac.nz
Fri Sep 1 21:10:23 EDT 2017 
Chris Angelico wrote:
> This particular example is safe, because the arguments get passed
> individually - so 'args' has one reference, plus there's one more for
> the actual function call

However, that's also true when you use the += operator,
so if the optimisation is to trigger at all in any useful
case, the refcount threshold needs to be set higher than
1.

Some experiments I did suggest that if you set it high
enough for x += y to trigger it, then it will also be
triggered in Joe's case.

BTW, isn't there already a similar optimisation somewhere
for concatenating strings? Does it still exist? How does
it avoid this issue?

-- 
Greg
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