Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder2.enfer-du-nord.net!newsfeed.eweka.nl!eweka.nl!feeder3.eweka.nl!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
MIME-Version: 1.0
In-Reply-To: <jclr1a$kjn$2@news.albasani.net>
References: <jclflh$u45$1@news.albasani.net> <mailman.3807.1324241477.27778.python-list@python.org> <jclr1a$kjn$2@news.albasani.net>
Date: Mon, 19 Dec 2011 10:40:06 +1100
Subject: Re: Newbie Question: Obtain element from list of tuples
From: Chris Angelico <rosuav@gmail.com>
To: python-list@python.org
Content-Type: text/plain; charset=ISO-8859-1
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.3808.1324251610.27778.python-list@python.org>
Lines: 35
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:17483

On Mon, Dec 19, 2011 at 9:55 AM, HoneyMonster <someone@someplace.invalid> wrote:
> When the user selects a row and clicks a button, I am using:
> pos = self.grid_1.GetGridCursorRow() to establish which tuple in recs is
> involved, and then pid = recs[pos][4] to determine the key value (I
> suspected that accessing recs directly would be more efficient that
> trying to determine the wxGrid column value, and in any case the pid is
> in recs but not in the wxGrid).

Yep, this looks like a sensible way to do it!

I would recommend, though, that you avoid "magic numbers" - the
process ID might happen to be in cell 4, but what if your column list
changes? This is especially problematic when you use "select * from
table", because changes outside your code can break things.

There's two solutions. One is to carefully match your SELECT statement
to a set of constants:

exec("SELECT FOO,BAR,QUUX,ASDF,PID,WHATEVER FROM table")
FOO,BAR,QUUX,ASDF,PID,WHATEVER,*_=range(20) # Cool trick to avoid
having to count the columns

But a better way is to let the database handle it. Check your
interface library to see if you can have it return dictionaries or
objects instead of tuples - then you could use:

pid = recs[pos]["pid"]
# or
pid = recs[pos]->pid

which avoids the need to count columns at all.

Other than that, though, yep - your code concept looks fine.

ChrisA