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Re: Newbie Question: Obtain element from list of tuples

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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

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Newbie Question: Obtain element from list of tuples HoneyMonster <someone@someplace.invalid> - 2011-12-18 19:41 +0000
  Re: Newbie Question: Obtain element from list of tuples Arnaud Delobelle <arnodel@gmail.com> - 2011-12-18 19:49 +0000
  Re: Newbie Question: Obtain element from list of tuples Roy Smith <roy@panix.com> - 2011-12-18 15:04 -0500
    Re: Newbie Question: Obtain element from list of tuples HoneyMonster <someone@someplace.invalid> - 2011-12-18 20:22 +0000
      Re: Newbie Question: Obtain element from list of tuples Roy Smith <roy@panix.com> - 2011-12-18 15:25 -0500
    Re: Newbie Question: Obtain element from list of tuples alex23 <wuwei23@gmail.com> - 2011-12-18 18:35 -0800
      Re: Newbie Question: Obtain element from list of tuples Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-19 03:00 +0000
        Re: Newbie Question: Obtain element from list of tuples "Frank Millman" <frank@chagford.com> - 2011-12-19 08:46 +0200
          Re: Newbie Question: Obtain element from list of tuples DevPlayer <devplayer@gmail.com> - 2011-12-19 07:37 -0800
          Re: Newbie Question: Obtain element from list of tuples alex23 <wuwei23@gmail.com> - 2011-12-19 19:53 -0800
  Re: Newbie Question: Obtain element from list of tuples Chris Angelico <rosuav@gmail.com> - 2011-12-19 07:51 +1100
    Re: Newbie Question: Obtain element from list of tuples Roy Smith <roy@panix.com> - 2011-12-18 16:10 -0500
    Re: Newbie Question: Obtain element from list of tuples HoneyMonster <someone@someplace.invalid> - 2011-12-18 22:55 +0000
      Re: Newbie Question: Obtain element from list of tuples Chris Angelico <rosuav@gmail.com> - 2011-12-19 10:40 +1100
        Re: Newbie Question: Obtain element from list of tuples HoneyMonster <someone@someplace.invalid> - 2011-12-20 00:59 +0000

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