Python counting the unique occurences of a string in a file

Question

I'm trying to count the unique IP addresses in a Apache log-file using python 3.3.1 The thing is I don't think that it is counting everything correctly.

Here is my code:

import argparse
import os
import sys
from collections import Counter

#
# This function counts the unique IP adresses in the logfile
#
def print_unique_ip(logfile):
    IPset = set()
    for line in logfile:
        head, sep, tail = line.partition(" ")
        if(len(head) > 1):
            IPset.update(head)

    print(len(IPset))
    return  

#
# This is the main function of the program
#
def main():
    parser = argparse.ArgumentParser(description="An appache log file processor")

    parser.add_argument('-l', '--log-file', help='This is the log file to work on', required=True)
    parser.add_argument('-n', help='Displays the number of unique IP adresses', action='store_true')
    parser.add_argument('-t', help='Displays top T IP adresses', type=int)
    parser.add_argument('-v', help='Displays the number of visits of a IP adress')

    arguments = parser.parse_args()

    if(os.path.isfile(arguments.log_file)):
        logfile = open(arguments.log_file)
    else:
        print('The file <', arguments.log_file, '> does not exist')
        sys.exit

    if(arguments.n == True):
        print_unique_ip(logfile)
    if(arguments.t):
        print_top_n_ip(arguments.t, logfile)
    if(arguments.v):
        number_of_ocurrences(arguments.v, logfile)

    return


if __name__ == '__main__':
  main()

I have left put everything else.

When I run it I get

$ python3 assig4.py -l apache_short.log -n
12

But I know that there are more than 12 unique IPs in the file

It doesn't seem to be giving me the right result. What I am trying to do is to read the file line by line, then when I find an IP address I put it into a set as it only saves unique elements and then I print out the length of said set.

Answer 1

IPset.update(head)

Bug. This will not do what you're expecting. You want to add each IP to your set instead. Examples make it clearest:

>>> s1 = set()
>>> s2 = set()
>>> s1.add('11.22.33.44')
>>> s2.update('11.22.33.44')
>>> s1
set(['11.22.33.44'])
>>> s2
set(['1', '3', '2', '4', '.'])