This functionality has existed since the earliest days of Python, and even if we all agreed it was wrong we couldn't change it -- it would just break too much existing code. I can't quite remember why I did it that way but it was definitely a conscious choice; probably some symmetry or edge case. (Note that it works this way at the other end too -- a.insert(-100, x) will insert x at the beginning of a, if a has fewer than 100 elements.)
On Mon, Sep 15, 2014 at 3:29 PM, Mark Shannon <m...@hotpy.org> wrote: > > > On 15/09/14 12:31, Tal Einat wrote: > >> On Mon, Sep 15, 2014 at 6:18 AM, Harish Tech <technews.f...@gmail.com> >> wrote: >> >>> I had a list >>> >>> a = [1, 2, 3] >>> >>> when I did >>> >>> a.insert(100, 100) >>> >>> [1, 2, 3, 100] >>> >>> as list was originally of size 4 and I was trying to insert value at >>> index >>> 100 , it behaved like append instead of throwing any errors as I was >>> trying >>> to insert in an index that did not even existed . >>> >>> >>> Should it not throw >>> >>> >>> IndexError: list assignment index out of range >>> >>> >>> exception as it throws when I attempt doing >>> >>> >>> a[100] = 100 >>> >>> Question : 1. Any idea Why has it been designed to silently handle this >>> instead of informing the user with an exception ? >>> >>> >>> Personal Opinion : Lets see how other dynamic languages behave in such a >>> situation : Ruby : >>> >>> >>> > a = [1, 2] >>> >>> > a[100] = 100 >>> >>> > a >>> >>> => [1, 2, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, >>> nil, >>> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, >>> nil, >>> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, >>> nil, >>> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, >>> nil, >>> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, >>> nil, >>> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, >>> nil, >>> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, 100] >>> >>> The way ruby handles this is pretty clear and sounds meaningful (and >>> this is >>> how I expected to behave and it behaved as per my expectation) at least >>> to >>> me . So what I felt was either it should throw exception or do the way >>> ruby >>> handles it . >>> >>> >>> Is ruby way of handling not the obvious way ? >>> >>> I even raised it in stackoverflow >>> http://stackoverflow.com/questions/25840177/list- >>> insert-at-index-that-is-well-out-of-range-behaves-like-append >>> >>> and got some responses . >>> >> >> Hello Harish, >> >> The appropriate place to ask questions like this is python-list [1], >> or perhaps Stack Overflow. >> > > I think this is an OK forum for this question. > If someone isn't sure if something is a bug or not, then why not ask here > before reporting it on the bug tracker? > > This does seem strange behaviour, and the documentation for list.insert > gives no clue as to why this behaviour was chosen. > > Cheers, > Mark. > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/ > guido%40python.org > -- --Guido van Rossum (python.org/~guido)
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