How to remove subset from a file efficiently?

[fynali]

    $ cat cleanup.py
    #!/usr/bin/python

    postpaid_file = open('/home/oracle/stc/test/PSP0000333')
    outfile = open('/home/oracle/stc/test/PSP-CBR.dat', 'w')

    barred = {}

    for number in open('/home/oracle/stc/test/CBR0000333'):
        barred[number] = None # just add it as a key

    outfile.writelines([number for number in postpaid_file if number
not in barred])

    postpaid_file.close(); outfile.close()

    --
    $ time ./cleanup.py

    real    0m31.007s
    user    0m24.660s
    sys     0m3.550s

Can we say that using generators & newer Python _is_ faster?

-- 
fynali