Extracting XML data from a tree

perlvroom has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to get an attribute from a certain part of an XML based on another attribute in the element above.

<?xml version="1.0" encoding="utf-8"?>
  <Month>
    <Week>
      <Day day-of-week="Monday">
        <Times>
          <Time start-time="01:00"/>
        </Times>
      </Day>
      <Day day-of-week="Tuesday">
        <Times>
          <Time start-time="02:00"/>
        </Times>
      </Day>
      <Day day-of-week="Wednesday">
        <Times>
          <Time start-time="03:00"/>
        </Times>
      </Day>
      <Day day-of-week="Thursday">
        <Times>
          <Time start-time="04:00"/>
        </Times>
      </Day>
      <Day day-of-week="Friday">
        <Times>
          <Time start-time="05:00"/>
        </Times>
      </Day>
      <Day day-of-week="Sunday">
        <Times>
          <Time start-time="06:00"/>
        </Times>
      </Day>
    </Week>
    
  </Month>
[download]

Here is the code i have so far:

use XML::Twig;
use strict;
use warnings;


 my $twig=XML::Twig->new();    
  $twig->parsefile( 'CC.xml'); 

my $data   = $twig->first_elt( 'Day' );
my $times   = $twig->first_elt( 'Time' );

my $day = $data->att( 'day-of-week' );
my $time = $times->att('start-time');

if ($day='Tuesday')
{
    print $time;
}
[download]

I basically want to be able to get the "start-time" attribute for whichever day i specify.

Comment on Extracting XML data from a tree Select or Download Code

Replies are listed 'Best First'.
Re: Extracting XML data from a tree by toolic (Bishop) on Jun 04, 2013 at 13:58 UTC
You could use a handler: `use XML::Twig; use strict; use warnings; my $twig = XML::Twig->new(twig_handlers => { Day => \&Day }); $twig->parsefile('CC.xml'); exit; sub Day { my ( $twig, $day ) = @_; if ($day->att('day-of-week') eq 'Tuesday') { print $day->first_child('Times')->first_child('Time')->att('st +art-time'), "\n"; } } __END__ 02:00` [download]	[reply] [d/l]
Re^2: Extracting XML data from a tree by perlvroom (Acolyte) on Jun 04, 2013 at 20:14 UTC
Thanks! This did exactly what i needed.	[reply]
Re: Extracting XML data from a tree by Neighbour (Friar) on Jun 04, 2013 at 14:22 UTC
The handler toolic describes is capable of working with large files. Alternatively, you could use xpath: `#!/usr/bin/perl use strict; use warnings; use XML::Twig; use v5.10; my $twig = XML::Twig->new(); $twig->parsefile( 'CC.xml'); my $looking_for_day = 'Tuesday'; foreach my $node ($twig->get_xpath('//Day[@day_of_week="' . $looking_f +or_day . '"]/Times/Time')) { say $node->att('start-time'); }` [download]	[reply] [d/l]
Re^2: Extracting XML data from a tree by toolic (Bishop) on Jun 04, 2013 at 14:29 UTC
One small correction: change day_of_week to day-of-week: `foreach my $node ($twig->get_xpath('//Day[@day-of-week="' . $looking_f +or_day . '"]/Times/Time')) {` [download]	[reply] [d/l]
Re^3: Extracting XML data from a tree by Neighbour (Friar) on Jun 04, 2013 at 14:50 UTC
Whoops, yes...I had a bit of trial and error getting it to work, and changed the -'s to _'s, but forgot to change them back when posting the code. Thanks for the correction.	[reply]
Re: Extracting XML data from a tree by hdb (Monsignor) on Jun 04, 2013 at 14:43 UTC
Not Twig but Simple: `use strict; use warnings; use XML::Simple; my $xml = XMLin( 'CC.xml' ); for (@{ $xml->{Week}{Day} }) { print $_->{Times}{Time}{'start-time'},"\n" if $_->{'day-of-week'} eq + "Tuesday"; }` [download]	[reply] [d/l]
Re^2: Extracting XML data from a tree by Jenda (Abbot) on Jun 05, 2013 at 08:30 UTC
See Simpler than XML::Simple. Your code would break if there were multiple <Time> tag in one <Times>. Here's one of the ways to do this with XML::Rules. It handles the multiple <Time> tags and stops processing the XML once it finds the requested day. use strict; use XML::Rules; use Data::Dumper; my $parser = XML::Rules->new( strispaces => 7, rules => { Time => 'as array', Times => 'pass', 'Day' => sub { my ($tag_name, $attrs, $context, $parent_data, $parser) = +@_; if ($attrs->{'day-of-week'} eq $parser->{parameters}) { $parser->return_this(join(', ', grep( defined($_), map + $_->{'start-time'}, @{$attrs->{Time}}))); } }, Month => sub{} } ); my $time = $parser->parse(\DATA, 'MondayX'); print "Time: $time\n"; __DATA__ <?xml version="1.0" encoding="utf-8"?> <Month> <Week> [download] Jenda Enoch was right!* Enjoy the last years of Rome.	[reply] [d/l]
Re^3: Extracting XML data from a tree by hdb (Monsignor) on Jun 05, 2013 at 08:51 UTC
Agreed. The story does not look as favorable for `XML::Simple` anymore if the structure changes. If one makes it more robust using `ForceArray => 1`, then at least one more loop is required: `my $xml = XMLin( 'CC.xml', ( ForceArray => 1 ) ); for my $day (@{ $xml->{Week}[0]{Day} }) { next unless $day->{'day-of-week'} eq "Tuesday"; for my $time ( @{ $day->{Times}[0]{Time} } ) { print $time->{'start-time'},"\n" if exists $time->{'start-time'}; } }` [download] Not really so "simple" anymore...	[reply] [d/l] [select]
Re: Extracting XML data from a tree by choroba (Cardinal) on Jun 05, 2013 at 08:34 UTC
Using XML::XSH2, a wrapper around XML::LibXML: `open CC.xml ; echo //Day[@day-of-week="Tuesday"]/Times/Time/@start-time ;` [download] لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l]