Performance of int/long in Python 3

[Steven D'Aprano]

On Sat, 06 Apr 2013 14:58:23 -0700, Ethan Furman wrote:

> On 04/06/2013 02:24 PM, Chris Angelico wrote:
>> On Sat, Apr 6, 2013 at 8:09 PM, Serhiy Storchaka <storchaka at gmail.com>
>> wrote:
>>> 04.04.13 00:57, Chris Angelico написав(ла):
>>>> http://bugs.python.org/issue17629 opened.
>>>
>>>
>>> See also the discussion at
>>> http://comments.gmane.org/gmane.comp.python.ideas/15640 . I agree with
>>> rejection. This is an implementation detail and different Python
>>> implementations (including future CPython versions) can have different
>>> internal string implementations.
>>
>> I really don't see why this means that there can't be a function in
>> sys, or something. I mean, other Pythons aren't expected to return the
>> exact same values from sys.getsizeof, are they?
> 
> What it boils down to is:
> 
>    - it can easily be done by hand now

For some definition of "easily".

if implementation == "CPython":
    if version < "3.3":
        if sys.maxunicode exists:
            use it to decide whether this is a wide or narrow build
            if a wide build: return 4
            else: return 2
        else:
            ???
    elif version == "3.3":
        scan the string, in some efficient or inefficient way
        return 1, 2, 4 depending on the largest character you find
    else:
        ???
else:
    ???



>    - it's a very uncommon need


Well, that at least is true. But then, needing to know the platform 
you're running under, the size of objects, the id of a object, the 
largest integer, the largest float, or the number of references seen by 
the garbage collector are also uncommon needs. What really matters is not 
how often you need it, but what you can do when you need it if you don't 
have it.



-- 
Steven