9.4

# #!/usr/bin/python
#
# By dvdjaco
# Exercise 9.4
#

f = raw_input('Enter a file name: ')

try:
    fhand = open(f)
except IOError, err :
        print "Error opening file", f
        print "Error was:", err
d = dict()

# build a dictionary with all email addresses and count the number of messages
# sent from each one
for line in fhand:
    words = line.split()
    if len(words) == 0 or words[0] != 'From' or words[1].find('@') == -1: continue
    d[words[1]] = d.get(words[1],0) + 1

# find who sent max messages
maxmessages = None
for sender in d:
    if maxmessages is None or d[sender] > maxmessages:
        maxmessages = d[sender]
        maxsender = sender

print d
print maxsender, "has sent", maxmessages, "messages"