Algorithm for Labels like in Gmail

[rhcarvalho at gmail.com]

Hello there!

I'm trying to make a simple Contact Manager using python (console
only), however i'm having trouble implementing a division by "Groups"
or "Labels" just like in Gmail. I don't have any real code to post
because all i got now is a raw TXT file holding the names and phones of
my contacts.

The only idea I could figure out until now seems too weak, so that's
why i'm asking for help. I thought of making a separate list (in a text
file) holding all the possible groups, where each group hold the names
of the contacts. Then if i access a group, i'll be able to see all
contacts related to that group. On the other hand, i'll also need to
attach to the contact instance a list of every group it is present.
I think it's a bad idea because it seems to be very easy to get things
messed up. Like I can get things corrupted or bad linked, and i'll
always need to run functions to check all the realations between
contact names and groups...

I like the way i can "label" emails on Gmail, does anyone know how I
can implement such kind of feature? What's the best/broadly used
algorithm?

Sorry for the long message, and thanks in advance

Rodolfo Carvalho