On Apr 11, 2013, at 6:52 PM, Ram Rachum 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.

Explicit utility functions are better than implicit special-case behaviors. Why should a string be special-cased to attribute lookup rather than, say, __getitem__ lookup?

Right, these are options too. I'd guess that attribute lookup is more common, but maybe I'm wrong.

Carl _______________________________________________ Python-ideas mailing list Python...@python.org http://mail.python.org/mailman/listinfo/python-ideas _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

Special cases aren't special enough to break the rules. ----------------- Donald Stufft PGP: 0x6E3CBCE93372DCFA // 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA

On 11 April 2013 23:52, Ram Rachum 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

Interesting! On Fri, Apr 12, 2013 at 2:33 AM, Haoyi Li 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@gmail.com> wrote:

...

On 11 April 2013 23:52, Ram Rachum 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 _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

Awesome module! On Fri, Apr 12, 2013 at 2:58 AM, João Bernardo 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

...

Interesting!

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

...

On 11 April 2013 23:52, Ram Rachum 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 _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

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Very crafty! I liked the idea of funcbuilder f as replacement for lambdas and the result is true pythonic! 2013/4/11 João Bernardo

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

...

Awesome module!

On Fri, Apr 12, 2013 at 2:58 AM, João Bernardo 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

...

Interesting!

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

...

On 11 April 2013 23:52, Ram Rachum 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 _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

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-- Carlo Pires

On Fri, Apr 12, 2013 at 11:41 AM, Antoine Pitrou wrote:

Le Fri, 12 Apr 2013 09:48:57 +1000, Steven D'Aprano a écrit :

...

So... -1 on allowing key='string' shortcuts, +0 on allowing key=3 shortcuts.

-1 on both :-)

Make that a -2 on both. Yuval