[Python-ideas] `OrderedDict.sort`

[Ram Rachum]

On Tue, Sep 24, 2013 at 7:27 PM, Andrew Barnert <abarnert at yahoo.com> wrote:

> On Sep 24, 2013, at 8:51, Ram Rachum <ram at rachum.com> wrote:
>
> I get your point. It's a nice idea. But I think it's slightly less elegant
> to create another dict. So I think it's almost as good as having a `.sort`
> method, but not quite as nice.
>
>
> Honestly, I think having a sorted mapping in the stdlib would be even
> nicer in almost any situation where this might be nice. But, given that we
> don't have such a thing, and getting one into the stdlib is harder than it
> appears, maybe that's not an argument against your (obviously simpler) idea.
>

For the record, I think that having a SortedDict in the stdlib would be
awesome.


>
> Of course in most cases, you just want to iterate once in sorted order,
> and it's hard to beat this:
>
>     for k, v in sorted(o.items()):
>

I think that in most of my cases it won't work. Either because I iterate in
Django templates, or I iterate several times which would make this
cumbersome and wasteful.


>
> (By the way, couldn't you make the same argument about `list.sort`?)
>
>
> You could. Except that list.sort predates sorted. And it's faster and
> saves memory, which isn't true of your suggestion. I don't know if that
> would be enough to add it today, but it's more than enough to keep it
> around.
>
> On Tue, Sep 24, 2013 at 6:49 PM, M.-A. Lemburg <mal at egenix.com> wrote:
>
>> On 24.09.2013 17:23, Ram Rachum wrote:
>> > Ethan, you've misunderstood my message and given a correct objection to
>> an
>> > argument I did not make.
>> >
>> > I did not argue against ordering by insertion order on init. I agree
>> with
>> > that decision. I disagree with defining the entire class as an insertion
>> > ordering class and refusing to allow users to reorder it as they wish
>> after
>> > it's created.
>>
>> The overhead introduced by completely recreating the internal
>> data structure after the sort is just as high as creating a
>> new OrderedDict, so I don't understand why you don't like about:
>>
>> from collections import OrderedDict
>> o = OrderedDict(((3,4), (5,4), (1,2)))
>> p = OrderedDict(sorted(o.iteritems()))
>>
>> This even allows you to keep the original insert order should
>> you need it again. If you don't need this, you can just use:
>>
>> o = dict(((3,4), (5,4), (1,2)))
>> p = OrderedDict(sorted(o.iteritems()))
>>
>> which is also faster than first creating an OrderedDict and
>> then recreating it with sorted entries.
>>
>> Put those two lines into a function and you have:
>>
>> def SortedOrderedDict(*args, **kws):
>>     o = dict(*args, **kws)
>>     return OrderedDict(sorted(o.iteritems()))
>>
>> p = SortedOrderedDict(((3,4), (5,4), (1,2)))
>>
>> --
>> Marc-Andre Lemburg
>> eGenix.com
>>
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