[Python-ideas] Allow key='attribute_name' to various sorting functions

[Ram Rachum]

Interesting!


On Fri, Apr 12, 2013 at 2:33 AM, Haoyi Li <haoyi.sg at gmail.com> wrote:

> A more generic and useful thing would be kind of what scala/groovy have:
> shorthands for defining function literals:
>
> Groovy:
> myList.sort{it.startTime}
>
> Scala:
> myList.sort(_.startTime)
>
> Where "_.startTime" and "it.startTime" are shorthand for "x =>
> x.startTime" or python's "lambda x: x.startTime". You could probably get
> something similar in python:
>
> sorted(entries, key = x.datetime_created)
>
> if you did some magic with x to make looking up an attribute return a
> lambda that returns that attribute of its argument.
>
> -Haoyi
>
>
>
> On Thu, Apr 11, 2013 at 7:05 PM, Oscar Benjamin <
> oscar.j.benjamin at gmail.com> wrote:
>
>> On 11 April 2013 23:52, Ram Rachum <ram.rachum at gmail.com> wrote:
>> > On Friday, April 12, 2013 1:35:20 AM UTC+3, Carl Meyer wrote:
>> >>
>> >> On 04/11/2013 04:24 PM, Ram Rachum wrote:
>> >> > I often want to sort objects by an attribute. It's cumbersome to do
>> >> > this:
>> >> >
>> >> >     sorted(entries, key=lambda entry: entry.datetime_created)
>> >> >
>> >> > Why not allow this instead:
>> >> >
>> >> >     sorted(entries, key='datetime_created')
>> >>
>> >>     from operator import attrgetter
>> >>     sorted(entries, key=attrgetter('datetime_created'))
>> >>
>> >> You can alias attrgetter to an even shorter name if you like.
>> >
>> > That's still cumbersome in my opinion.
>>
>> I don't think it's that cumbersome. Leaving aside the import line
>> you're only having to specify two things for your key function: that
>> it's an attribute (attrgetter) and the name of the attribute
>> ('datetime_created'). It's not possible for this to be any more
>> succinct without using special case implicit rules which are generally
>> a bad thing. I like the fact that the API for the sorted function is
>> so simple I can remember all of its arguments and exactly what they do
>> without ever needing to look it up.
>>
>>
>> Oscar
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>
>
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