[Tutor] IP sorting

[Roman Suzi]

On Thu, 27 Dec 2001, Karthik Gurumurthy wrote:

> this one is cool and so was danny's.
> i have a question here though.
> 
> why do we need to convert to a tuple?
> 
> lot = [tuple(map(int, ip.split("."))) for ip in iplist]
> 
> is there any specific reason. Python does not know to sort a list of lists?

Tuple is a constant list. It is slightly faster to deal with tuples. In my
version I am using standard sort() method, which is much faster "as is"
than when it is using ANY cmp function.

"lot" is a list. I am applying .sort() to it to sort it.

IP adresses has sort order different from their string
representation. Another way to sort them is:

----------------------------------------------------
from socket import inet_aton, inet_ntoa

iplist = [
          "195.168.1.123",
          "192.168.1.123",
          "192.168.1.111",
          "192.168.1.11",
          ]

lot = map(inet_aton, iplist)
lot.sort()
iplist1 = map(inet_ntoa, lot)

print iplist1

------------------------------------------------------ 

Of course, it is possible to write cmp function as easy as:

def cmpIPAddresses(a, b):
    return cmp(inet_aton(a), inet_aton(b))


That is, one can use the most compact version of IP-addresses
comparison:

from socket import inet_aton
  iplist.sort(lambda a, b: cmp(inet_aton(a), inet_aton(b)))


Function socket.inet_aton converts symbolical IP-address into 4-byte
string, which can be compared by common rules.

> karthik.

Sincerely yours, Roman A.Suzi
-- 
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