[Python-ideas] Fast sum() for non-numbers - why so much worries?

[Terry Reedy]

On 7/11/2013 1:53 AM, Ronald Oussoren wrote:
>
> On 11 Jul, 2013, at 7:27, Stephen J. Turnbull <stephen at xemacs.org> wrote:

>> It does count; it's a language change.  It is not a bug-fix in which
>> the implementation is brought into line with the language definition.
>
> That doesn't mean that using += instead of + in sum isn't a valid change
> to make for 3.4.

Breaking code in the way this would do, would require a PEP and 
deprecation cycle. I do not anticipate approval for a general change.

A specialized change such that sum(iterable_of_lists, []) would extend 
rather than replace [] might be done since the result would be equal to 
the current result, just faster, and since [] must be nearly always 
passed without aliases that depend on it not changing. Even that should 
have a deprecation warning.

Tuples could be linearly summed in a list with .extend and then 
converted at the end. I don't believe that would be a semantic change at 
all.

> BTW. This thread has been rehashing the same arguments over and over again,
> and it's pretty likely that most core devs have stopped following this thread

Right, I just happened to pick this post because you are also a core dev.

> because of that.  It's probably time for someone to write a summary
> the discussion (what are the proposals and the arguments in favor and against them)

-- 
Terry Jan Reedy