Op 12-09-16 om 23:29 schreef Chris Angelico:
> On Tue, Sep 13, 2016 at 7:19 AM, BartC <b...@freeuk.com> wrote:
>> By the same argument, then strings and ints are also mutable.
>>
>> Here, the original tuple that a refers to has been /replaced/ by a new one.
>> The original is unchanged. (Unless, by some optimisation that recognises
>> that there are no other references to it, the original is actually appended
>> to. But in general, new objects are constructed when implementing +=.)
> And by definition, that optimization cannot be detected. At best, all
> you could do is something like:
>
> old_id = id(a)
> a += something
> if id(a) == old_id:
> print("We may have an optimization, folks!")
>
> But that can have false positives. If two objects do not concurrently
> exist, they're allowed to have the same ID number.
You could do the following:
old_a = a
a += something
if old_a is a:
print("We have an optimization, folks!")
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