Lists inside dictionary and how to look for particular value

[Gregory Ewing]

mick verdu wrote:
> What I want is if host already exists it would
> overwrite otherwise add to database. And if host doesn't exist it will first
> add this host to database and then compare its IP with IPs of rest of hosts.
> If ip matches with any of the other hosts, it will delete the host that it
> just added now.

It sounds like you should be maintaining two dictionaries:

    hostname --> IP (+ other host-related data)

    IP --> hostname

Given a (newhost, newip) pair, first look for newip in the
IP --> hostname dictionary.

If it's there and the old hostname equals newhost, you're
finished.

If it's there with a different hostname, first delete
that entry from IP --> hostname, and also delete the
old hostname from hostname --> IP.

Now add tne new entry to both dictionaries.

-- 
Greg