How can one detect which tables are in a database?

In Postgresql I could do:
def   listTables(conn):
   """   given a database connection, list the tables included in that 
database  """
   sql   =  \
      """select c.relname FROM pg_catalog.pg_class c
         LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
         WHERE c.relkind IN ('r','') AND n.nspname NOT IN ('pg_catalog', 
'pg_toast')
         AND pg_catalog.pg_table_is_visible(c.oid);
      """
   cur   =  conn.cursor()
   cur.execute(sql)
   tables   =  cur.fetchall()
   return   list( (tbl[0]  for   tbl   in tables) )

but this is dependent upon various features of Postgresql.  Still, it 
shows the kind of function I'm after.  Any suggestions?  Any references?