exercise11_2.py

"""
Exercise  11.2: Write a program to look for lines of the form

'New Revision: 39771'

and extract the number from each of the lines using a regular expression and
the findall() method. Compute the average of the numbers and print out the
average.

Enter file:mbox.txt
38549.7949721

Enter file:mbox-short.txt
39756.9259259

Python for Everybody: Exploring Data Using Python 3
by Charles R. Severance

Solution by Jamison Lahman, June 4, 2017
"""
import re

fname = input('Enter file:')
try:
    fhand = open(fname)
except:
    print('File cannot be opened:', fname)
    exit()

rev = []
for line in fhand:
    line = line.rstrip()
    rev_temp = re.findall('^New Revision: ([0-9.]+)', line)
    if rev_temp != []:
        for val in rev_temp:
            val = float(val)            #Convert the strings to floats
            rev = rev + [val]           #Concats new values
        
rev_sum = sum(rev)
count = float(len(rev))
rev_ave = rev_sum / count

print(rev_ave)