Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Date: Sat, 28 Mar 2015 09:55:57 +1100
From: Cameron Simpson <cs@zip.com.au>
To: Manuel Graune <manuel.graune@koeln.de>
Cc: python-list@python.org
Subject: Re: Supply condition in function call
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Disposition: inline
In-Reply-To: <87twx6qkdz.fsf@uriel.graune.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
References: <87twx6qkdz.fsf@uriel.graune.org>
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.281.1427496970.10327.python-list@python.org>
Lines: 49
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:88186

On 27Mar2015 21:02, Manuel Graune <manuel.graune@koeln.de> wrote:
>Cameron Simpson <cs@zip.com.au> writes:
>
>> This passes the local variables inside test1() to "condition" as a
>> single parameter. Now, I grant that vars['i'] is a miracle of
>> tediousness. So consider this elaboration:
>>
>>  from collections import namedtuple
>>
>>  condition_test = lambda vars: vars.i + vars.j > 4
>>
>>  def test1(a, b, condition):
>>    for i, j in zip(a,b):
>>      c = i + j
>>      vars = locals()
>>      varnames = list(vars.keys())
>>      varstupletype = namedtuple("locals", varnames)
>>      varstuple = varstupletype(*[ vars[k] for k in varnames ])
>>      if condition(varstuple):
>>        print("Foo")
>>
>> Here, the condition_test function/lambda uses "vars.i" and "vars.j",
>> which i think you'll agree is easier to read and write. The price is
>> the construction of a "namedtuple" to hold the variable name
>> values. See:
>>
>>  https://docs.python.org/3/library/collections.html#collections.namedtuple
>>
>
>This is probably getting off topic,

I think it is on topic.

>but is there any relevant difference
>or benefit to using namedtuple instead of something like types.SimpleNamespace?
>
>https://docs.python.org/3/library/types.html#additional-utility-classes-and-functions

Probably not. SimpleNamespace is much easier to construct; I hadn't thought of 
it. As the doc remarks, a namedtuple is probably better for fixed records (eg 
mapping out rows of a CSV file) because it will prevent you using the wrong 
name. But for a comparison function SimpleNamespace is probably better.

Cheers,
Cameron Simpson <cs@zip.com.au>

The Horn of Vengeance: When he pushes the horn button, the device produces
the sound of fingernails scraping on a blackboard, amplified beyond pain
threshold.  If that doesn't work, the horn then plays the Pina Colada song.