lists <-> tuple

[Peter Notebaert]

I am new to Python and have to create an import library in C that uses
matrices.

These matrices can be one-dimensional (vectors) or two-dimensional. If I
look in the ActivePython 2.4 documentation at data structures, then I see at
least 2 posibilities to represent them: Lists and Tuples.

The documention doesn't give me much information on what the best choice is
for the data type to provide/return these matrices.

So my question is, should I use lists or tuples to represent my matrices in
and why?

Thanks for any reaction.

[Jim]

Re: lists &lt;-&gt; tuple

> Tuples or lists for matrix-like functionality?

Use lists. Tuples are meant for small immutable sets of things that go
together. Lists are more like arrays, and you can assign to one
existing element if you want.

One exception, is a short vector is often a tuple like (x, y, z) and
you might want to multiply that vector by your matrix. You can convert
a tuple to a list with list(aTuple) or back with tuple(aList.)

Even better, take a look at numarray (or numpy or scipy or scipy_core.)
They all have really nice matrix code and there are C APIs that let
you manipulate them. Chances are they do everything you're intending
to implement.

Immutability example:
tup = ("a", "b", "c")
tup[1] = "g"
Traceback (most recent call last):
File "<input>", line 1, in ?
TypeError: object does not support item assignment
lst = ["a", "b", "c"]
lst[1] = "g"
lst
['a', 'g', 'c']


-Jim

[Robert Kern]

Re: lists &lt;-&gt; tuple

Peter Notebaert wrote:[color=blue]
> I am new to Python and have to create an import library in C that uses
> matrices.
>
> These matrices can be one-dimensional (vectors) or two-dimensional. If I
> look in the ActivePython 2.4 documentation at data structures, then I see at
> least 2 posibilities to represent them: Lists and Tuples.
>
> The documention doesn't give me much information on what the best choice is
> for the data type to provide/return these matrices.
>
> So my question is, should I use lists or tuples to represent my matrices in
> and why?[/color]

You'll probably want to use scipy_core. It's a package designed
specifically to deal with multidimensiona l arrays of homogeneous,
(usually) numeric data.

http://numeric.scipy.org

--
Robert Kern
rkern@ucsd.edu

"In the fields of hell where the grass grows high
Are the graves of dreams allowed to die."
-- Richard Harter

[Peter Notebaert]

Re: lists &lt;-&gt; tuple


"Jim" <mrmaple@gmail. com> wrote in message
news:1130973892 .137886.170410@ f14g2000cwb.goo glegroups.com.. .[color=blue][color=green]
>> Tuples or lists for matrix-like functionality?[/color]
>
> Use lists. Tuples are meant for small immutable sets of things that go
> together. Lists are more like arrays, and you can assign to one
> existing element if you want.
>
> One exception, is a short vector is often a tuple like (x, y, z) and
> you might want to multiply that vector by your matrix. You can convert
> a tuple to a list with list(aTuple) or back with tuple(aList.)
>
> Even better, take a look at numarray (or numpy or scipy or scipy_core.)
> They all have really nice matrix code and there are C APIs that let
> you manipulate them. Chances are they do everything you're intending
> to implement.
>
> Immutability example:
> tup = ("a", "b", "c")
> tup[1] = "g"
> Traceback (most recent call last):
> File "<input>", line 1, in ?
> TypeError: object does not support item assignment
> lst = ["a", "b", "c"]
> lst[1] = "g"
> lst
> ['a', 'g', 'c']
>
>
> -Jim
>[/color]

Thanks!

[Peter Notebaert]

Re: lists &lt;-&gt; tuple


"Robert Kern" <robert.kern@gm ail.com> wrote in message
news:mailman.47 .1130974709.187 01.python-list@python.org ...[color=blue]
> Peter Notebaert wrote:[color=green]
>> I am new to Python and have to create an import library in C that uses
>> matrices.
>>
>> These matrices can be one-dimensional (vectors) or two-dimensional. If I
>> look in the ActivePython 2.4 documentation at data structures, then I see
>> at
>> least 2 posibilities to represent them: Lists and Tuples.
>>
>> The documention doesn't give me much information on what the best choice
>> is
>> for the data type to provide/return these matrices.
>>
>> So my question is, should I use lists or tuples to represent my matrices
>> in
>> and why?[/color]
>
> You'll probably want to use scipy_core. It's a package designed
> specifically to deal with multidimensiona l arrays of homogeneous,
> (usually) numeric data.
>
> http://numeric.scipy.org
>
> --
> Robert Kern
> rkern@ucsd.edu
>
> "In the fields of hell where the grass grows high
> Are the graves of dreams allowed to die."
> -- Richard Harter
>[/color]

Thanks!