Begineer Question : Global string substitution with re

[peter leonard]

Thank you the prompt reply. It works now.... a definite begineer question.

Peter


>From: Gary Herron <gherron at islandtraining.com>
>Reply-To: gherron at islandtraining.com
>To: "peter leonard" <pfleonard at hotmail.com>, python-list at python.org
>Subject: Re: Begineer Question : Global string substitution with re
>Date: Mon, 22 Sep 2003 02:40:06 -0700
>
>On Monday 22 September 2003 02:22 am, peter leonard wrote:
> > Hi,
> > This is a basic question but I can't figure out what is wron - even 
>after
> > reading the documentation. I have a script that normalizes strings. One 
>of
> > the steps is to convert all fractions too the tag 'fraction'. For 
>example :
> >
> > import re
> > line = "This is the first ratio, 170/37, and this is the second  170/37 
>"
> >
> >
> > def normalise(text):
> >
> >     #Tag fractions
> >     fraction = r'(\s+\d+\/\d+\s+)'
> >     regfr = re.compile(fraction)
> >     text = regfr.sub(" |fraction| ",text)
> >
> >     #Remove punctuation
> >     punc = r'\,'
> >     regpunc = re.compile(punc)
> >     text = regpunc.sub("",text)
> >
> >     return text
> >
> > print line,"\n"
> > print normalise(line),"\n"
> >
> >
> > The output from this script is :
> >
> > This is the first ratio, 170/37, and this is the second  170/37
> >
> > This is the first ratio 170/37 and this is the second |fraction|
> >
> >
> > I can't understand why only one of the fractions gets substituted. The
> > documentation for sub states that the default argument for sub is 0 
>which
> > means replace all occurences. The output of my script should be :
> >
> > This is the first ratio |fraction| and this is the second |fraction|
>
>The problem is that your regular expression ends with "\s+".  This means
>the digits of the fraction *must* be followed by at least one space,
>and the digits of your first fraction are followed by a comma and not
>a space.
>
>Your re is matching spaces--fraction--spaces.  I'd guess that you
>don't really want to match spaces on either side of the fraction.
>
>Gary Herron
>
>

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