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

[João Bernardo]

You can have something like that with this module I created:
     https://github.com/jbvsmo/funcbuilder

from funcbuilder import f
sorted(entries, key=f.datetime_created)


Some features in this module are *very* experimental, but are also very
cool...


João Bernardo


2013/4/11 Ram Rachum <ram.rachum at gmail.com>

> 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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>>> Python-ideas at python.org
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>>>
>>
>>
>
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