authentication

Hi,

I'm using PostgreSQL 7.4.3 on i386-pc-linux-gnu, compiled by GCC
i386-linux-gcc (GCC) 3.3.4 (Debian 1:3.3.4-3).

I'm fine with most things except I simply don't understand how authentication
works - I have RTFM'd and still don't get it. I have no trouble connecting
with the Postmaster on my local machine via command-line psql, but I'm not
experiencing the same joy with Python or PgAccess, both return similar errors
if I specify the Host as 'localhost':

Python:
_pg.error: FATAL: IDENT authentication failed for user "tim"
and something very similar from PgAccess, which I don't appear to be able to
cut & paste. I'm sure it's trivially simple, if anyone could point me to a
clear explanation of how to do this on a GNU system, I'd be grateful.

cheers

tim hall