|
[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]
|
Re: [PLUG] python, lambda, map
|
Jeff,
I think the problem is that the list returned from foo is a RHS value
(term?). Many other languages generate compile time, or run time
errors when you attempt to modify a value like this.
Python allows you to operate on RHS values and to good benefit. It
gives you the ability to write "/n".join([1, 2, 3,4]), etc.
In your case the list is probably being created as you expected, it is
just transient and you never see it - remember list.extent() modifies
a list in place, and doesn't return the list.
Because extend doesn't return a list, you need something else. Try using '+':
L = map(lambda x: foo(x) + foo(x+2), L)
Hope this helps a little.
Kevin
On Sun, 17 Oct 2004 19:52:27 -0400, Jeff Abrahamson <jeff@purple.com> wrote:
> In the below, I want L=[3,4,5,6] at the end. Clearly that's not
> what's happening.
>
> The problem is that I want to use a map with a lambda form, so I can't
> make assignments.
>
> >>> def foo(x):
> ... return [x,x+1]
> ...
> >>> foo(3)
> [3, 4]
> >>> foo(3).extend(foo(5))
> >>> L=foo(3).extend(foo(5))
> >>> L
> >>>
>
> I want to write something like this:
>
> L = map(lambda x: foo(x).extend(foo(x+2)), L)
>
> Any thoughts?
>
> I might have to break down and name this function...
>
> --
> Jeff
>
> Jeff Abrahamson <http://www.purple.com/jeff/> +1 215/837-2287
> GPG fingerprint: 1A1A BA95 D082 A558 A276 63C6 16BF 8C4C 0D1D AE4B
>
> A cool book of games, highly worth checking out:
> http://www.amazon.com/exec/obidos/ASIN/1931686963/purple-20
>
>
>
___________________________________________________________________________
Philadelphia Linux Users Group -- http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug
|
|