On Thu, 05 Nov 2015 11:54:20 +1100, Steven D'Aprano
<st...@pearwood.info> wrote:
>On Thu, 5 Nov 2015 10:02 am, Seymore4Head wrote:
>
>> So far the only use I have for regex is to replace slicing, but I
>> think it is an improvement.
>
>I don't understand this. This is like saying "so far the only use I have for
>a sandwich press is to replace my coffee pot". Regular expressions and
>slicing do very different things.
>
>Slicing extracts substrings, given known starting and ending positions:
>
>
>py> the_str = "Now is the time for all good men..."
>py> the_str[7:12]
>'the t'
>
>
>Regular expressions don't extract substrings with known start/end positions.
>They *find* matching text, giving a search string with metacharacters. (If
>there are no metacharacters in your search string, you shouldn't use a
>regex. str.find will be significantly faster and more convenient.)
>
>Slicing is not about finding text, it is about extracting text once you've
>already found it. So they are complementary, not alternatives.
Here is an example of the text we are slicing apart.
>From stephen.marqu...@uct.ac.za Sat Jan 5 09:14:16 2008
Return-Path: <postmas...@collab.sakaiproject.org>
Received: from murder (mail.umich.edu [141.211.14.90])
by frankenstein.mail.umich.edu (Cyrus v2.3.8) with LMTPA;
Sat, 05 Jan 2008 09:14:16 -0500
X-Sieve: CMU Sieve 2.3
Received: from murder ([unix socket])
by mail.umich.edu (Cyrus v2.2.12) with LMTPA;
Sat, 05 Jan 2008 09:14:16 -0500
Received: from holes.mr.itd.umich.edu (holes.mr.itd.umich.edu
[141.211.14.79])
by flawless.mail.umich.edu () with ESMTP id m05EEFR1013674;
Sat, 5 Jan 2008 09:14:15 -0500
Received: FROM paploo.uhi.ac.uk (app1.prod.collab.uhi.ac.uk
[194.35.219.184])
BY holes.mr.itd.umich.edu ID 477F90B0.2DB2F.12494 ;
5 Jan 2008 09:14:10 -0500
Received: from paploo.uhi.ac.uk (localhost [127.0.0.1])
by paploo.uhi.ac.uk (Postfix) with ESMTP id 5F919BC2F2;
Sat, 5 Jan 2008 14:10:05 +0000 (GMT)
Message-ID: <200801051412.m05eciah010...@nakamura.uits.iupui.edu>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Received: from prod.collab.uhi.ac.uk ([194.35.219.182])
by paploo.uhi.ac.uk (JAMES SMTP Server 2.1.3) with SMTP ID
899
for <sou...@collab.sakaiproject.org>;
Sat, 5 Jan 2008 14:09:50 +0000 (GMT)
Received: from nakamura.uits.iupui.edu (nakamura.uits.iupui.edu
[134.68.220.122])
by shmi.uhi.ac.uk (Postfix) with ESMTP id A215243002
for <sou...@collab.sakaiproject.org>; Sat, 5 Jan 2008
14:13:33 +0000 (GMT)
Received: from nakamura.uits.iupui.edu (localhost [127.0.0.1])
by nakamura.uits.iupui.edu (8.12.11.20060308/8.12.11) with
ESMTP id m05ECJVp010329
for <sou...@collab.sakaiproject.org>; Sat, 5 Jan 2008 09:12:19
-0500
Received: (from apache@localhost)
by nakamura.uits.iupui.edu (8.12.11.20060308/8.12.11/Submit)
id m05ECIaH010327
for sou...@collab.sakaiproject.org; Sat, 5 Jan 2008 09:12:18
-0500
Date: Sat, 5 Jan 2008 09:12:18 -0500
X-Authentication-Warning: nakamura.uits.iupui.edu: apache set sender
to stephen.marqu...@uct.ac.za using -f
To: sou...@collab.sakaiproject.org
From: stephen.marqu...@uct.ac.za
The practice problems are something like pull out all the email
addresses or pull out the days of the week and give the most common.
--
https://mail.python.org/mailman/listinfo/python-list
