Question

I have a file of IP addresses called “IPs”. When I parse a new IP from my logs, I’d like to see if the new IP is already in file IPs, before I add it. I know how to add the new IP to the file, but I’m having trouble seeing if the new IP is already in the file.

!/usr/bin/python
from IPy import IP
IP = IP('192.168.1.2')
#f=open(IP('IPs', 'r'))  #This line doesn't work
f=open('IPs', 'r')    # this one doesn't work 
for line in f:
    if IP == line:
       print "Found " +IP +" before"
f.close()

In the file “IPs”, each IP address is on it’s own line. As such:

222.111.222.111
222.111.222.112

Also tried to put the file IPs in to an array, but not having good luck with that either.
Any ideas?

Thank you,

Gary

Answer 1

iplist = []

# With takes care of all the fun file handling stuff (closing, etc.)
with open('ips.txt', 'r') as f:
    for line in f:
        iplist.append(line.strip())   # Gets rid of the newlines at the end

# Change the above to this for Python versions < 2.6
f = open('ips.txt', 'r')
for line in f:
    iplist.append(line.strip())
f.close()

newip = '192.168.1.2'

if newip not in iplist:
    f = open('ips.txt', 'a') # append mode, please
    f.write(newip+'\n')

Now you have your IPs in a list (iplist) and you can easily add your newip to it iplist.append(newip) or do anything else you please.

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Edit:

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If you’re worried about programming being difficult, there’s a book that’s geared towards kids, but I honestly found it both easy-to-digest and informative.
Snake Wrangling for Kids

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Alan Gauld, one of the foremost contributors to the [e-mail] mailing list has this tutorial that’s really good and also is adapted to Python 3. He also includes some other languages for comparison.

If you want a good dead-tree book, I’ve heard that Core Python Programming by Wesley Chun is a really good resource. He also contributes to the python tutor list every so often.

The tutor list is another good place to learn about python – reading, replying, and asking your own questions. I actually learned most of my python by trying to answer as many of the questions I could. I’d seriously recommend subscribing to the tutor list if you want to learn Python.