[Tutor] .sort(key = ???)

[Dave S]

On Thursday 16 November 2006 22:35, John Fouhy wrote:
> On 17/11/06, Dave S <pythontut at pusspaws.net> wrote:
> > Hi,
> >
> > I have a bunch of lists within lists that I need to sort ref item [4], I
> > can't access my code at the moment but I basically ...
>
> [...]
>
> > Having googled I think there is a better way of doing this with the key
> > attribute
> >
> > a.sort(key= ?? )
>
> Yep, that's right.  You need at least python2.4 for this, though.
>
> You need to pass the key= parameter a function that will take an
> element of your list, and return the comparison key.
>
> eg:
>
> def item4(elem):
>     return elem[4]
>
> a.sort(key=item4)
>
> Since this is a common thing to do, there is a function in the
> operator module that you can use, instead of defining your own:
>
> import operator
> a.sort(key=operator.itemgetter(4))
>
> (operator.itemgetter(4) will return a function that is basically
> equivalent to item4() above)
>
> HTH!

Sure does - cheers

Dave