[Tutor] urllib problem

[Roelof Wobben]

----------------------------------------
> From: steve at pearwood.info
> To: tutor at python.org
> Date: Wed, 13 Oct 2010 01:51:16 +1100
> Subject: Re: [Tutor] urllib problem
>
> On Tue, 12 Oct 2010 11:58:03 pm Steven D'Aprano wrote:
> > On Tue, 12 Oct 2010 11:40:17 pm Roelof Wobben wrote:
> > > Hoi,
> > >
> > > I have this programm :
> > >
> > > import urllib
> > > import re
> > > f =
> > > urllib.urlopen("http://www.pythonchallenge.com/pc/def/linkedlist.ph
> > >p? nothing=6") inhoud = f.read()
> > > f.close()
> > > nummer = re.search('[0-9]', inhoud)
> > > volgende = int(nummer.group())
> > > teller = 1
> > > while teller <= 3 :
> > > url =
> > > "http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=" +
> > > str(volgende) f = urllib.urlopen(url)
> > > inhoud = f.read()
> > > f.close()
> > > nummer = re.search('[0-9]', inhoud)
> > > print "nummer is", nummer.group()
> > > volgende = int(nummer.group())
> > > print volgende
> > > teller = teller + 1
> > >
> > > but now the url changes but volgende not.
> > > What do I have done wrong ?
> >
> > Each time through the loop, you set volgende to the same result:
> >
> > nummer = re.search('[0-9]', inhoud)
> > volgende = int(nummer.group())
> >
> > Since inhoud never changes, and the search never changes, the search
> > result never changes, and volgende never changes.
>
> Wait, sorry, inhoud should change... I missed the line inhoud = f.read()
>
> My mistake, sorry about that. However, I can now see what is going
> wrong. Your regular expression only looks for a single digit:
>
> re.search('[0-9]', inhoud)
>
> If you want any number of digits, you need '[0-9]+' instead.
>
>
> Starting from the first URL:
>
> >>> f = urllib.urlopen(
> ... "http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=6")
> >>> inhoud = f.read()
> >>> f.close()
> >>> print inhoud
> and the next nothing is 87599
>
>
> but:
>
> >>> nummer = re.search('[0-9]', inhoud)
> >>> nummer.group()
> '8'
>
> See, you only get the first digit. Then looking up the page with
> nothing=8 gives a first digit starting with 5, and then you get stuck
> on 5 forever:
>
> >>> urllib.urlopen(
> ... "http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=8").read()
> 'and the next nothing is 59212'
> >>> urllib.urlopen(
> ... "http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=5").read()
> 'and the next nothing is 51716'
>
>
> You need to add a + to the regular expression, which means "one or more
> digits" instead of "a single digit".
>
>
>
> --
> Steven D'Aprano
> _______________________________________________
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Hoi Steven, 
 
Finally solved this puzzle.
Now the next one of the 33 puzzles.
 
Roelof