Referencing Items in a List of Tuples

[rshepard at nospam.appl-ecosys.com]

  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