On Fri, Jul 31, 2020 at 7:59 PM Steven D'Aprano <st...@pearwood.info> wrote:
> On Fri, Jul 31, 2020 at 04:08:43PM -0700, Guido van Rossum wrote: > [...] > > I'm guessing that indexing by 0, if it were possible, would be a > convenient > > idiom to implement the "first item" operation that has been requested > > numerous times (at least for dicts). > > Indeed, that seems to be the only use-case which seems to be even > remotely common. `dict.popitem` would do it, of course, but it also > mutates the dict. > > The other simple solution is `next(iter(mydict.items()))`. > That one always makes me uncomfortable, because the StopIteration it raises when the dict is empty might be misinterpreted. Basically I never want to call next() unless there's a try...except StopIteration: around it, and that makes this a lot less simple. > The bottom line here seems to me, as far as I can tell, is that being > able to fetch a key and/or value by index is of only marginal use. > Agreed. > > Slicing would be useful to get the > > first N items of a huge dict without materializing the full list of items > > as a list object, which brought Chris B to request this in the first > place. > > The first request in this thread was from Hans: > > > https://mail.python.org/archives/list/python-ideas@python.org/message/S7UMTWK65X6BJDYZ3SSU7I7HOIASDMMJ/ > > He is using a dict to hold an array of columns indexed by name > `{column_name: column}` and wanted to re-order and insert columns at > arbitrary positions. > A bare dict is just not the data structure for that problem. -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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