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Python Programming Language
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Referencing Items in a List of Tuples
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
On Feb 25, 3:01 am, rshep@nospam.appl-ecosys.com wrote:
> 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.
for item in mainlist:
if item[0] == 'eco' and item[1] == 'con':
ec.append(item[2:])
if you want numeric adressing, try:
for i in range(len(mainlist)):
if mainlist[i][0] == 'eco' etc.
On Feb 25, 1:01 pm, rshep@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':
so do this:
if item[0] == 'eco' and item[1] == 'con':
> ec.Append(mainlist[item][2:])
and
ec.append(item[2:]) # note append, not Append
> python doesn't like a non-numeric index.
irrespective of what you do :-)
> I would really appreciate a pointer
Sorry, only nasty languages have pointers :-)
> so I can learn how to manipulate lists
> of tuples by referencing specific items in each tuple (string or float).
HTH,
John
"Rune Strand" <rune.str @gmail.com> writes: > if you want numeric adressing, try: > for i in range(len(mainlist)): > if mainlist[i][0] == 'eco' etc.
for i,m in enumerate(mainlist):
if m[0] == 'eco' etc.
On 25 Feb 2007 02:01:18 GMT, rshep@nospam.appl-ecosys.com declaimed
the following in comp.lang.python:
> 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.
for tpl in mainlist:
if tpl[0] == "eco" and tpl[1] == "con":
ec.Append(tpl[2:]) #presuming ec is NOT a list, as Append()
#is not a list method (append() is)
--
Wulfraed Dennis Lee Bieber KD6MOG
wlfr@ix.netcom.com wulfr@bestiaria.com
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: web-a@bestiaria.com)
HTTP://www.bestiaria.com/
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