assignment 11.2

import re
hand = open('mbox-short.txt')
nums = list()
for line in hand:
    line = line.rstrip()
    x = re.findall('New Revision: ([0-9]+)',line)
    if len(x) == 1 :
        val = float(x[0])
        nums.append(val)
print sum(nums)/len(nums)