Help with cumulative sum

[Maggie]

Building on the code that I posted in one of the previous posts.. I
need to find a cumulative sum of the file of the times in the test
file:

here is the code i have:

#!/usr/bin/python

import os.path

#name of output file
filename = "OUTPUT.txt"

#open the file
test = open ("test.txt", "rU")

#read in all the data into a list
readData = test.readlines()

count = 0

FILE = open(filename, "w")

for item in readData:

   count = count + 1
   tmp_string = str(count) + '	' + item
   print >> FILE, tmp_string,

else:
   print 'The loop is finito'

-----

my test file is this

23
241
34234
83
123

and I need to find a CUMULATIVE sum (or the running sum)...what would
be the best way to go about that given the code i already have?

thank you all!