HTM::TreeBuilder, HTML::Element's look

7stud has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

When I parse a string of html that I conjured up looking for span tags that have the attribute class="value", this code works:

use strict;
use warnings;
use 5.010;

use LWP::Simple;
use HTML::TreeBuilder;

my $html =<<'END_HTML';
<html>
<head><title></title></head>
<body>
<div><span class="value">Hi</span></div>
<p>Thanks</p>
<div><span class="value">Hello</span></div>
</body>
</html>
END_HTML


my $tree = HTML::TreeBuilder->new_from_content($html);
my @spans = $tree->look_down(class => 'value');


for my $span (@spans) {
    say $span->as_trimmed_text();
}

$tree->delete();


--output:--
Hi
Hello
[download]

But when I unleash my code in the wild, it doesn't find the span tags:

use strict;
use warnings;
use 5.010;

use LWP::Simple;
use HTML::TreeBuilder;

my $url = 'http://www.almanac.com/weather/history/zipcode/21218/2008-0
+9-02';

my $html = get($url);


my $tree = HTML::TreeBuilder->new();
$tree->parse_file($html);

my $span_tag = $tree->look_down(
    class => 'value',
);

say $span_tag->as_trimmed_text();

$tree->delete();

--output:--
Can't call method "as_trimmed_text" on an undefined value at 1perl.pl 
+line 41.
[download]

Can anyone see what the problem is?

Thanks

Comment on HTM::TreeBuilder, HTML::Element's look_down() method Select or Download Code

Replies are listed 'Best First'.
Re: HTM::TreeBuilder, HTML::Element's look_down() method by afresh1 (Hermit) on Oct 06, 2010 at 21:11 UTC
Pretty simple, `$html` is not a file, so `$tree->parse_file` won't work. Use `$tree->parse` instead. With some additional error checking it would have even give you a clue: `$tree->parse_file($html) or die $!;` l8rZ, -- andrew	[reply] [d/l] [select]
Re^2: HTM::TreeBuilder, HTML::Element's look_down() method by 7stud (Deacon) on Oct 06, 2010 at 21:24 UTC
Ah, thanks! And I could just use the same method as in the first example. The examples I looked at didn't use die(). I should have thought of that myself. Thanks again!	[reply]
Re^3: HTM::TreeBuilder, HTML::Element's look_down() method by afresh1 (Hermit) on Oct 06, 2010 at 21:45 UTC
If you had done the same as the first example, it should have worked as well, however I would still recommend checking that it was successful. `my $tree = HTML::TreeBuilder->new_from_content($html) or die $!;` l8rZ, -- andrew	[reply] [d/l]