Inconsistent result from request

Hi listers,

As a PG administrator, I'm trying to read technical data from pg_class table
to monitor tables and indexes space.

We are running a quite big postgres platform, with multiple databases,
multiples schemes in each database, and hundreds tables.

When I run the attach python script, I get 1809 rows as result. When I run
the included (from the script) select query from phpPgAdmin or pgAdmin III,
I get 2010 rows as result.

When I try to focus on specific table including where relname ='tablename'
in both parts of the join, I also get different numbers of rows. So I can't
have the full size of all indexes attached on a table.

Does anyone has a clue of why the same query, on same database gives
different result depending on it is included in a python script, or ran from
a console?

Many Thanks
Patrick