[Tutor] dynamic arrays?

[Brian Jones]

On Mon, Sep 27, 2010 at 11:39 AM, Alex Hall <mehgcap at gmail.com> wrote:

> On 9/27/10, Brian Jones <bkjones at gmail.com> wrote:
> > On Mon, Sep 27, 2010 at 11:32 AM, Alex Hall <mehgcap at gmail.com> wrote:
> >
> >> Hi all,
> >> One thing I have never much liked about Python is its need for
> >> specifically sized arrays and lack of a dynamic, array-like data
> >> structure. For example, the following fails with a "list assignment
> >> index out of range" error:
> >>
> >> a=[]
> >> i=0
> >> for l in open("file.txt", "r"):
> >>  a[i]=l
> >>   i+=1
> >>
> >
> > Is there some reason to use this construct rather than the list object's
> > 'append' method?
> >
> > for i in open('file.txt', 'r'):
> >     a.append(l)
>
> Ah, good thought. So exactly what are the functional differences
> between a list and an array in Python, or are they so close that it
> makes no difference which you use? It seems like you can index into
> both with the bracket notation. Are lists limited in any way that
> makes them not as desirable as arrays?
>

A python list and a python array are one and the same to my knowledge. Do
you mean a list and a dict? A dict is an unordered collection of key-value
pairs, and the keys are more or less arbitrary values of your own creation
(I believe the single limitation is the key must be a hashable type). A list
is a 'flat' array, although you can use enumerate(l) to get index->value
pairs from a list 'l'.

hth.



> >
> > brian
> >
> >>
> >> Is there something in Python I am missing that would let the above
> >> work? I am hoping that my annoyance at the apparent lack of such a
> >> thing is unfounded. BTW, I know why the above throws that exception.
> >> TIA.
> >>
> >> --
> >> Have a great day,
> >> Alex (msg sent from GMail website)
> >> mehgcap at gmail.com; http://www.facebook.com/mehgcap
> >> _______________________________________________
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> >
> >
> >
> > --
> > Brian K. Jones
> > My Blog          http://www.protocolostomy.com
> > Follow me      http://twitter.com/bkjones
> >
>
>
> --
> Have a great day,
> Alex (msg sent from GMail website)
> mehgcap at gmail.com; http://www.facebook.com/mehgcap
>



-- 
Brian K. Jones
My Blog          http://www.protocolostomy.com
Follow me      http://twitter.com/bkjones
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