Referencing Items in a List of Tuples

[Paddy]

On Feb 25, 5:44 pm, Jussi Salmela <tiedon_j... at hotmail.com> wrote:
> Paddy kirjoitti:
>
>
>
> > On Feb 25, 2:01 am, rshep... at nospam.appl-ecosys.com wrote:
> >>   While working with lists of tuples is probably very common, none of my
> >> five Python books or a Google search tell me how to refer to specific items
> >> in each tuple. I find references to sorting a list of tuples, but not
> >> extracting tuples based on their content.
>
> >>   In my case, I have a list of 9 tuples. Each tuple has 30 items. The first
> >> two items are 3-character strings, the remaining 28 itmes are floats.
>
> >>   I want to create a new list from each tuple. But, I want the selection of
> >> tuples, and their assignment to the new list, to be based on the values of
> >> the first two items in each tuple.
>
> >>   If I try, for example, writing:
>
> >> for item in mainlist:
> >>     if mainlist[item][0] == 'eco' and mainlist[item][1] == 'con':
> >>       ec.Append(mainlist[item][2:])
>
> >> python doesn't like a non-numeric index.
>
> >>   I would really appreciate a pointer so I can learn how to manipulate lists
> >> of tuples by referencing specific items in each tuple (string or float).
>
> >> Rich
>
> > You might also use list comprehensions to accumulate the values you
> > need:
>
> > ec = [ item[2:]  for item in mainlist  if item[:2] == ['eco','con'] ]
>
> > - Paddy.
>
> I'm nitpicking, but the OP has a list of tuples:
>
> ec = [ item[2:]  for item in mainlist  if item[:2] == ('eco','con') ]
>
> Cheers,
> Jussi

Of course. Ta.
- paddy.