Lucky numbers in Python

Cecil Westerhof Cecil at
Thu Apr 30 02:01:02 CEST 2015

Op Thursday 30 Apr 2015 00:38 CEST schreef Ian Kelly:

> On Wed, Apr 29, 2015 at 3:45 PM, Cecil Westerhof <Cecil at> wrote:
>> Op Wednesday 29 Apr 2015 21:57 CEST schreef Ian Kelly:
>>> And although it's not clear to me what this is supposed to be
>>> doing, you probably no longer need the middle term if the
>>> intention is to continue deleting all the way to the end of the
>>> list (if it is then I think you have a bug in the existing
>>> implementation, since the last item in the list can never be
>>> deleted).
>> What do you mean by this? Executing:
>> lucky_numbers(5)
>> gives:
>> [1, 3]
>> So the last element (5) is deleted.
> Off by one error on my part. This is why negative skip values on
> ranges and slices are not recommended: they're confusing. :-)
> In that case you can definitely omit the middle term of the slice,
> which will be both more concise and clearer in intent, though
> probably not significantly faster.

It is certainly nit faster. It is even significantly slower. With the
middle term lucky_numbers(int(1e6)) takes 0.13 seconds. Without it
takes 14.3 seconds. Hundred times as long.

Cecil Westerhof
Senior Software Engineer

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