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

[Carlo Pires]

Very crafty! I liked the idea of funcbuilder f as replacement for lambdas
and the result is true pythonic!


2013/4/11 João Bernardo <jbvsmo at gmail.com>

> It was something I did for fun, so I never had the time to add proper
> documentation.
> You can see the best examples to use by reading the doctests from __init__.
>
> BTW, It abuses a lot of Python 3 constructions, so you can't use Python 2.x
>
>
>
> João Bernardo
>
>
> 2013/4/11 Ram Rachum <ram.rachum at gmail.com>
>
>> Awesome module!
>>
>>
>> On Fri, Apr 12, 2013 at 2:58 AM, João Bernardo <jbvsmo at gmail.com> wrote:
>>
>>> 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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>>
>
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-- 
  Carlo Pires
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