Question about `list.insert`

Chris Angelico rosuav at gmail.com
Fri Feb 7 04:20:43 CET 2014


On Fri, Feb 7, 2014 at 2:11 PM, Tim Chase <python.list at tim.thechases.com> wrote:
> On 2014-02-06 22:00, Roy Smith wrote:
>> > list does not promise better than O(1) behavior
>>
>> I'm not aware of any list implementations, in any language, that
>> promises better than O(1) behavior for any operations.  Perhaps
>> there is O(j), where you just imagine the operation was performed?
>
> Pish...there's always O(0) which is achieved by *not* performing some
> unneeded operation ;-)
>
> -tkc

Ooh! Ooh! I got it!

class fast_list(list):
    def append(self,obj,randrange=random.randrange):
        if len(self) and randrange(len(self)): return
        return super().append(obj)

Repeated appends to this list are amortized O(0)!

ChrisA



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