The Code

#!/usr/local/bin/python

# /usr/local/bin/pg2gz.py

# This script lists all PostgreSQL
# databases and pipes them separately
# through gzip into .gz files.

# INSTRUCTIONS
# 1.  Review and edit line 1 to reflect the location
#     of your python command file.
# 2.  Redefine the save_dir variable (on line 22) to
#     your backup directory.
# 3.  To automate the backup process fully, consider
#     scheduling the regular execution of this script
#     using cron.

import os, string

# Redefine this variable to your backup directory.
# Be sure to include the slash at the end.
save_dir = '/mnt/backup/databases/'

# Rename all *.gz backup files to *.gz.old.
curr_files = os.listdir(save_dir)
for n in curr_files:
        if n[len(n)-2:] =  = 'gz':
                os.popen('mv ' + save_dir + n + " " + save_dir + n + '.old')
        else:
                pass

# Vacuum all databases
os.popen('vacuumdb -a -f -z')

# 'psql -l' produces a list of PostgreSQL databases.
get_list = os.popen('psql -l').readlines( )

# Exclude header and footer lines.
db_list = get_list[3:-2]

# Extract database names from first element of each row.
for n in db_list:
        n_row = string.split(n)
        n_db = n_row[0]

        # Pipe database dump through gzip
        # into .gz files for all databases
        # except template*.
        if n_db =  = 'template0':
                pass
        elif n_db =  = 'template1':
                pass
        else:
                os.popen('pg_dump ' + n_db + ' | gzip -c > ' + save_dir + 
                          n_db + '.gz')