Sorting email addresses by domain

[Jp Calderone]

On Thu, 11 Nov 2004 01:58:35 -0000, "Peter Murray" <pdmurray at ntlworld.com> wrote:
>Hi! I hope someone can assist me, I have been using Python for a year or
> two, but I am not a programmer and only use it occasionally for small issues
> or just for fun. So I perhaps do not have the right 'mindset' to always see
> the answer to a problem.
> 
> Anyway, I have a list of email address and I want to sort them by domain.
> List.sort() wont work as this looks at the start of each address only. So
> the answer I have come up with is to split each email address around the
> "@", swap the position of the name and domain, build a new list with these
> and then sort this. Then switch positions back, and join with an "@". It
> works, but it seems a little inelegant. Is there a better, or easier way to
> do this?

  In Python 2.3,

    def key(addr):
        parts = addr.split('@')
        parts.reverse()
        return parts
    addresses.sort(lambda a, b: cmp(key(a), key(b)))

  In Python 2.4, re-using the above definition of key:

    addresses.sort(key=key)

  Jp