exercise9_5.py

"""
Exercise  9.5: This program records the domain name (instead of the address)
where the message was sent from instead of who the mail came from (i.e., the
whole email address). At the end of the program, print out the contents of
your dictionary.

python schoolcount.py
Enter a file name: mbox-short.txt
['media.berkeley.edu': 4, 'uct.ac.za': 6, 'umich.edu': 7, 'gmail.com': 1, 
'caret.cam.ac.uk': 1, 'iupui.edu': 8}

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

Solution by Jamison Lahman, May 31, 2017
"""

dictionary_domains = dict()                       #Initializes the dictionary
fname = input('Enter file name: ')
try:
    fhand = open(fname)
except:
    print('File cannot be opened:', fname)
    exit()
    
for line in fhand:
    words = line.split()
    if len(words) == 0 or len(words) < 2 or words[0] != 'From': 
        continue
    else:
        atpos = words[1].find('@')               #position of the @ character
        domain = words[1][atpos+1:]              #stores the characters after the @
        if domain not in dictionary_domains:
            dictionary_domains[domain] = 1       #First entry
        else:
            dictionary_domains[domain] += 1      #Additional counts
            
print(dictionary_domains)