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References: <crvsfb-drf.ln1@chris.zbmc.eu> <mailman.14512.1412159108.18130.python-list@python.org> <cj2tfb-80s.ln1@chris.zbmc.eu>
Date: Wed, 1 Oct 2014 06:56:57 -0400
Subject: Re: How to show a dictionary sorted on a value within its data?
From: Joel Goldstick <joel.goldstick@gmail.com>
Cc: "python-list@python.org" <python-list@python.org>
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On Wed, Oct 1, 2014 at 6:45 AM,  <cl@isbd.net> wrote:
> Peter Otten <__peter__@web.de> wrote:
>> cl@isbd.net wrote:
>>
>> > I have a dictionary as follows:-
>> >
>> > {
>> > u'StarterAmps1': Row(id=3D4, ain=3Du'AIN3', name=3Du'StarterAmps1',
>> > conv=3D6834.374834509803, Description=3Du'Starter Amps'), u'LeisureVol=
ts':
>> > Row(id=3D1, ain=3Du'AIN0', name=3Du'LeisureVolts', conv=3D29.013742159=
95874,
>> > Description=3Du'Leisure Volts'), u'RudderPos': Row(id=3D6, ain=3Du'AIN=
5',
>> > name=3Du'RudderPos', conv=3D0.028125, Description=3Du'Rudder Position'=
), u'xx':
>> > Row(id=3D7, ain=3Du'AIN6', name=3Du'xx', conv=3D0.028125, Description=
=3Du''),
>> > u'LeisureAmps1': Row(id=3D3, ain=3Du'AIN2', name=3Du'LeisureAmps1',
>> > conv=3D32.727273081945, Description=3Du'Leisure Amps'), u'StarterVolts=
':
>> > Row(id=3D2, ain=3Du'AIN1', name=3Du'StarterVolts', conv=3D28.944696289=
11757,
>> > Description=3Du'Starter Volts') }
>> >
>> > I want to output a menu to a user comprising some parts of the
>> > dictionary (ain and Description) sorted by ain.
>> >
>> > Is there some incantation of sorted() that will do what I want?  I
>> > can't quite fathom out the 'key=3D' parameter needed to sort it by the
>> > tuple item.  Maybe I need a cmp=3D ?
>> >
>> > E.g. I want to do something like:-
>> >
>> >     for meas in sorted(adc.cfg, key=3D???):
>> >         print(adc.cfg[meas].ain, adc.cfg[meas].Description)
>> >
>> > What's needed in the ???
>>
>> for meas in sorted(adc.cfg, key=3Dlambda key: adc.cfg[key].ain):
>>     print(adc.cfg[meas].ain, adc.cfg[meas].Description)
>>
> Brilliant, worked perfectly, thank you.  The bit I didn't understamd was
> that 'lambda' bit, but I just looked it up and I'm a bit clearer now.
>
>> or simpler
>>
>> for row in sorted(adc.cfg.values(), key=3Doperator.attrgetter("ain"))
>>     print(row.ain, row.Description)
>>
> I tried this, I got:-
>
>     Traceback (most recent call last):
>       File "/home/chris/bin/calibrate.py", line 24, in <module>
>           for meas in sorted(adc.cfg.values,
>           key=3Doperator.attrgetter("ain")):
>           NameError: name 'operator' is not defined
> I must admit that it's the bits like 'operator' in the parameters that
> I can't really understand where they come from.
>

operator is a module. See
https://docs.python.org/2/library/operator.html#module-operator
>
>> or even
>>
>> for row in sorted(
>>         map(operator.attrgetter("ain", "Description"), adc.cfg.values())=
):
>>     print(*row)
>>
>
> --
> Chris Green
> =C2=B7
> --
> https://mail.python.org/mailman/listinfo/python-list



--=20
Joel Goldstick
http://joelgoldstick.com