exercise10_1.py

#!/usr/bin/env python3
"""
Exercise  10.1: Revise a previous program as follows: Read and parse the "From"
lines and pull out the addresses from the line. Count the number of messages
from each person using a dictionary.

After all the data has been read, print the person with the most commits by
creating a list of (count, email) tuples from the dictionary. Then sort the
list in the reverse order and print out the person who has the most commits.

Sample line:
From stephen.marquard@uct.ac.az Sat Jan 05 09:14:16 2008

Enter a file name: mbox-short.txt
cwen@iupui.edu 5

Enter a file name: mbox.txt
zqian@umich.edu 195

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


dictionary_addresses = dict()           # Initialize variables
lst = list()

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

for line in fhand:
    words = line.split()
    if len(words) < 2 or words[0] != 'From':
        continue
    else:
        if words[1] not in dictionary_addresses:
            dictionary_addresses[words[1]] = 1       # First entry
        else:
            dictionary_addresses[words[1]] += 1      # Additional counts

for key, val in list(dictionary_addresses.items()):
    lst.append((val, key))              # Fills list with value, key of dict

lst.sort(reverse=True)                  # Sorts by highest value

for count, email in lst[:1]:            # Only displays the largest value
    print(email, count)