help understanding class or function

[andrew cooke]

Vincent Davis wrote:
> I guess I am thinking of it as an operation that I am preforming on a list
> and not making a new list. Also looking to learn better methods. This is
> difficult when you are working alone. It is difficult to know where to
> improve.

python occupies a strange place.  in some ways it encourages a style of
programming that takes ideas from functional programming, and at other
times from object oriented programming.

here you are drifting towards a more functional approach.  in such
languages it's often quite normal to return new lists, and for the pattern
  a = somefunc(a)
to occur.

this seems a bit odd if you're used to objects modifying themselves
in-place, or concerned with performance.  but it's not necessarily bad
style in python.

this may be a somewhat personal viewpoint - just throwing it out in case
it helps.  you might find looking at ML or Scheme or Erlang useful
later...

andrew

> The actual functions I am making are more complicated than this example.
> Thanks
> Vincent Davis
> 720-301-3003
>
>
> On Thu, Mar 5, 2009 at 5:13 PM, Gabriel Genellina
> <gagsl-py2 at yahoo.com.ar>wrote:
>
>> En Thu, 05 Mar 2009 14:43:12 -0200, Vincent Davis <
>> vincent at vincentdavis.net> escribió:
>>
>>
>>  If I have a list and I what to make changes to it.a =
>> [1,2,3,4,5,6,7,8,9]
>>> and maybe I want to drop the odd and double the  even numbers and I
>>> will
>>> need to do this repeatedly.
>>> How is this best done? That is as a function or class. All I know how
>>> to
>>> do
>>> is
>>>
>>> def doubleeven(alist):
>>>    blist = [2*x for x in a if x % 2 ==0]
>>>   return blist
>>>
>>> then when I am using it I do this
>>>
>>> a = doubleeven(a)
>>> I what to keep it named "a"
>>>
>>> I am not sure if this is the best way in terms of format or structure.
>>> Is
>>> there a better way.
>>>
>>
>> I don't grasp what you're worried about... Your function does exactly
>> what
>> you have specified above, so it's correct. Don't you like the fact that
>> it
>> returns a *new* list instead of modifying the original one in-place? You
>> may
>> use:
>>
>> a[:] = doubleeven(a)
>>
>> Or rewrite the function using a while loop (to avoid having two lists
>> alive
>> at the same time), but I would not bother unless there are strong
>> reasons
>> (the lists is really huge, or there is very few memory available).
>>
>> --
>> Gabriel Genellina
>>
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
> --
> http://mail.python.org/mailman/listinfo/python-list
>