[Tutor] Modifying a QIF

[Eduardo Vieira]

Hello, this weekend I had fun using Python for text processing. I
needed to change a qif converted from a ofx, using the tool MT2OFX
(http://www.xs4all.nl/~csmale/mt2ofx/en/index.htm)
I wanted to change transactions like these:
D11/14/2008
MCHEQUE 102 17590807;Cheque or Preauth. Debit
T-500.00
N102
^

Into this:
D11/14/2008
MCHEQUE 102 17590807;Cheque or Preauth. Debit
T-500.00
N102
PLorne Koehn
LHousing:Rent

== That is, insert those given Payee and Category if the transaction
was a cheque of 500.00

I came up with these two versions and would like to know which should
be more efficient or practical. Could you point improvements?
VERSION ONE:
f = open('cibc.QIF', 'r').readlines()
for line in range(len(f)):
    if f[line] == 'T-500.00\n':
        f[line+1] += 'PLorne Koehn\nLHousing:Rent\n'

new = open('cibc.QIF', 'w')
new.writelines(f)

VERSION TWO:
f = open('cibc.QIF', 'rw')
g = open('newresult.qif', 'w')
flag = 0
for line in f:
    if line == 'T-500.00\n':
        flag = 1
    elif line.startswith('N') and flag:
        flag = 0
        line += 'PLorne Koehn\nLHousing:Rent\n'

    g.write(line)

f.close()

#======

    One thing like about version 1 is that I can overwrite the same
file, and don't need to create another one. I haven't figured out how
to do the same with the second version and overcoming the IOError.

Thanks for your attention

Edu