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Groups > comp.lang.python > #63899

Re: What's correct Python syntax?

From Roy Smith <roy@panix.com>
Newsgroups comp.lang.python
Subject Re: What's correct Python syntax?
Date 2014-01-14 08:34 -0500
Organization PANIX Public Access Internet and UNIX, NYC
Message-ID <roy-BA6517.08343114012014@news.panix.com> (permalink)
References <mailman.5437.1389689219.18130.python-list@python.org>

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In article <mailman.5437.1389689219.18130.python-list@python.org>,
 Igor Korot <ikorot01@gmail.com> wrote:

> Hi, ALL,
> I'm trying to process a file which has following lines:
> 
> 192.168.1.6 > 192.168.1.7: ICMP echo request, id 100, seq 200, length 30
> 
> (this is the text file out of tcpdump)
> 
> Now I can esily split the line twice: once by ':' symbol to separate
> address and the protocol information and the second time by ',' to get
> information about the protocol.
> However, I don't need all the protocol info. All I'm interested in is
> the last field, which is length.

One possibility would be to forget about all the punctuation and just 
use "length " (note the trailing space) as the split delimiter:

>>> line = '192.168.1.6 > 192.168.1.7: ICMP echo request, id 100, seq 
200, length 30'
>>> line.split('length ')
'30'

this will only work if you're sure that "length " can never appear 
anywhere else in the line.  Another, perhaps more idiomatic, way would 
be:

>>> _, length = line.split('length ')
>>> print length
30

What's happening here is split() is returning a list of two items, which 
you then unpack into two variables, "_" and "length".  It's common to 
unpack unwanted fields into "_", as a hint (to the reader) that it's 
unused.

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Thread

What's correct Python syntax? Igor Korot <ikorot01@gmail.com> - 2014-01-14 00:46 -0800
  Re: What's correct Python syntax? Rustom Mody <rustompmody@gmail.com> - 2014-01-14 00:54 -0800
    Re: What's correct Python syntax? Igor Korot <ikorot01@gmail.com> - 2014-01-14 01:25 -0800
      Re: What's correct Python syntax? Rustom Mody <rustompmody@gmail.com> - 2014-01-14 01:37 -0800
        Re: What's correct Python syntax? Igor Korot <ikorot01@gmail.com> - 2014-01-14 02:02 -0800
          Re: What's correct Python syntax? Rustom Mody <rustompmody@gmail.com> - 2014-01-14 02:16 -0800
            Re: What's correct Python syntax? Igor Korot <ikorot01@gmail.com> - 2014-01-14 02:35 -0800
              Re: What's correct Python syntax? Rustom Mody <rustompmody@gmail.com> - 2014-01-14 02:51 -0800
          Re: What's correct Python syntax? Roy Smith <roy@panix.com> - 2014-01-14 08:47 -0500
        Re: What's correct Python syntax? Peter Otten <__peter__@web.de> - 2014-01-14 12:33 +0100
        Re: What's correct Python syntax? Ned Batchelder <ned@nedbatchelder.com> - 2014-01-14 07:19 -0500
        Re: What's correct Python syntax? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-14 08:58 -0500
    Re: What's correct Python syntax? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-14 09:37 +0000
    Fwd: What's correct Python syntax? Igor Korot <ikorot01@gmail.com> - 2014-01-14 02:03 -0800
      Re: Fwd: What's correct Python syntax? Larry Hudson <orgnut@yahoo.com> - 2014-01-14 22:00 -0800
  Re: What's correct Python syntax? Alister <alister.ware@ntlworld.com> - 2014-01-14 10:59 +0000
  Re: What's correct Python syntax? Roy Smith <roy@panix.com> - 2014-01-14 08:34 -0500

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