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extracting sub elements from DOM by class

by Discipulus (Abbot)
on Mar 26, 2021 at 14:30 UTC ( #11130387=perlquestion: print w/replies, xml ) Need Help??

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

Hello folks,

I must admit: I dont understand the DOM and scraping websites is a pain if you dont know it.

I'm using Mojo::DOM to parse a document, but I want to select and grab some sub element too, specifying their class=

The following code is the best I was able to produce, but I want to know, for example, if a phone number comes from class="fa fa fa-phone" or class="fa fa fa-mobile-phone" (infact Francesco Petrarca has not a mobile) and I also want to grab the url of the avatar image.

I hope my code and data is not too big to read.

use strict; use warnings; use Mojo::DOM; my $data = join '',<DATA>; my $dom = Mojo::DOM->new( $data ); foreach my $memb ( $dom->find('[id="members-list"] li')->each ){ print "\n########\n"; my $writers_list = $memb ->find('*') ->map( 'text' ) ->grep( qr/\S/ ) ->join("\n") ; print $writers_list; } __DATA__ <ul id="members-list" class="item-list" role="main"> <li> <div class="item-avatar"> <a href="https://intra.example.com/coworkers/dantealighier +i/"><img src="SRCURL/></a> <span class="member-role">Sottoscrittore</span> + </div> <!-- .item-avatar --> <div class="item"> <div class="item-title"> <a href="https://intra.example.com/coworkers/dantealig +hieri/" class="heading"><h3>Dante Alighieri</h3></a> + </div> <div class="item-meta"><span class="activity">active 6 + days ago, 19 hours ago</span></div> <div class="woffice-xprofile-list"> <span><i class="fa fa fa-phone"></i>011111111</spa +n> <span><i class="fa fa fa-mobile-phone"></i>3333333 +33</span> <span><i class="fa fa fa-envelope-o"></i>dante.ali +ghieri@example.com</span> <span><i class="fa fa fa-check"></i>Poets and Writ +ers</span> </div> </div> <div class="action"></div> <div class="clear"></div> </li> <li> <div class="item-avatar"> <a href="https://intra.example.com/coworkers/francescopetr +arca/"><img src="SRCURL/></a> <span class="member-role">Sottoscrittore</span> + </div> <!-- .item-avatar --> <div class="item"> <div class="item-title"> <a href="https://intra.example.com/coworkers/francesco +ptetrarca/" class="heading"><h3>Francesco Petrarca</h3></a> + </div> <div class="item-meta"><span class="activity">active 7 + days ago, 22 hours ago</span></div> <div class="woffice-xprofile-list"> <span><i class="fa fa fa-phone"></i>02222222</span +> <span><i class="fa fa fa-mobile-phone"></i></span> <span><i class="fa fa fa-envelope-o"></i>francesco +.petrarca@example.com</span> <span><i class="fa fa fa-check"></i>Poets and Writ +ers</span> </div> </div> <div class="action"></div> <div class="clear"></div> </li> </ul>

In my mind I'd like to populate an hash like:

my %members = ( 'Dante Alighieri' => { 'avatar_url' => 'URL', 'fa fa fa-phone' => '02222222', 'fa fa fa-mobile-phone' => '333333333', 'fa fa fa-envelope-o' => 'dante.alighieri@example.com' 'fa fa fa-check' => 'Poets and Writers', }, ... );

L*

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

Replies are listed 'Best First'.
Re: extracting sub elements from DOM by class
by haukex (Bishop) on Mar 26, 2021 at 21:14 UTC
    I must admit: I dont understand the DOM and scraping websites is a pain if you dont know it.

    The basics of DOM are actually not all too difficult - it's basically a tree structure with nodes of different types. They're often represented as objects with a base "node" class that supports methods like "what are the children of this node", and the different node types are implemented as subclasses of this node (XML::LibXML works this way; Mojo::DOM AFAIK doesn't, but these are just implementation details). The two most common are "element" nodes, that represent <elements>s (including their attributes), and text nodes, that represent any text in between elements. There's also "comment" nodes that represent <!-- comments -->, etc.

    In my experience, probably one of the most common things to confuse people is that this structure is very formal and rigid, asking a question like "what is the text content of <p>Hello, <b>cool</b> World!</p>?" is not as obvious as one might think. This <p> element has three children: the text "Hello, ", the element <b>, and the text " World!". To get all the text content means to walk down the tree and include the text child node "cool" of the <b> element too. Most libraries have functions that do this for you though.

    Anyway, one nice thing about Mojo::DOM is that it supports CSS selectors. This is related to the DOM of course, but actually simplifies finding things in the DOM a lot. They're a little bit like a more flexible XPath. See Mojo::DOM::CSS: ids can be selected via #idname and classes can be selected via .classname, with automatic handling of multiple classes, e.g. your class="fa fa fa-mobile-phone" can be selected via e.g. .fa-mobile-phone or perhaps .fa.fa-mobile-phone, though interestingly I don't see a mention of the latter in the docs (it's in the W3C specs though).

    Your HTML appears to be structured as a class="item-list" with <div class="item">s containing the data, so that's what I'd start with. What I think is quite strange is <span><i class="fa fa fa-phone"></i>011111111</span>, it's unclear to me why the class="fa fa fa-phone" isn't on the <span> that actually contains the data but is instead on the empty <i> in front of it. But oh well, we can deal with that too. (Update: Oh, they're Font Awesome icons.)

    use Mojo::Base -strict, -signatures; use Mojo::DOM; use Mojo::Util qw/trim dumper/; my $dom = Mojo::DOM->new( do { local $/; <DATA> } ); my %members; $dom->find('#members-list .item')->map(sub { # assume only one .item-title (use ->find instead of ->at otherwis +e) my $name = trim( $_->at('.item-title')->all_text ); $_->find('.woffice-xprofile-list .fa')->map(sub { my $class = $_->attr('class'); # go up one node from the <i> to the <span> my $content = $_->parent->all_text; # assume no duplicates $members{$name}{$class} = $content; }); }); print dumper(\%members);
Re: extracting sub elements from DOM by class
by tangent (Vicar) on Mar 26, 2021 at 18:20 UTC
    I'm not familiar with Mojo::DOM but this is how I would do it using HTML::TreeBuilder::XPath. If you don't know them already you will need to learn some Xpath expressions, but that is a useful thing to know.

    Note that <i class="fa fa fa-phone"></i> does not actually contain the phone number - it is a FontAwesome element that displays an icon - so you need to go up one level to get the content: $phone_icon->parent->as_text. Same goes for all the other FontAwesome elements.

    You may need to add checks for elements that are missing in some members. PS: I had to fix the image source in your example.

    use Data::Dumper; use HTML::TreeBuilder::XPath; my $data = join '', <DATA>; my $tree = HTML::TreeBuilder::XPath->new; $tree->parse($data); $tree->eof; my %members; my @items = $tree->findnodes('//ul[@id="members-list"]/li'); for my $item (@items) { my ($member_link) = $item->findnodes('div/div[@class="item-title"] +/a'); my $member = $member_link->as_text; my ($avatar_img) = $item->findnodes('div[@class="item-avatar"]/a/i +mg'); my $avatar = $avatar_img->attr('src'); my ($phone_icon) = $item->findnodes('div//i[@class="fa fa fa-phone +"]'); my $phone = $phone_icon->parent->as_text; my ($mobile_icon) = $item->findnodes('div//i[@class="fa fa fa-mobi +le-phone"]'); my $mobile = $mobile_icon->parent->as_text; $members{$member} = { 'avatar_url' => $avatar, 'fa fa fa-phone' => $phone, 'fa fa fa-mobile-phone' => $mobile, }; } print Dumper(\%members); __DATA__ <ul id="members-list" class="item-list" role="main"> <li> <div class="item-avatar"> <a href="https://intra.example.com/coworkers/dantealighier +i/"><img src="SRCURL"></a> <span class="member-role">Sottoscrittore</span> + </div> <!-- .item-avatar --> <div class="item"> <div class="item-title"> <a href="https://intra.example.com/coworkers/dantealig +hieri/" class="heading"><h3>Dante Alighieri</h3></a> + </div> <div class="item-meta"><span class="activity">active 6 + days ago, 19 hours ago</span></div> <div class="woffice-xprofile-list"> <span><i class="fa fa fa-phone"></i>011111111</spa +n> <span><i class="fa fa fa-mobile-phone"></i>3333333 +33</span> <span><i class="fa fa fa-envelope-o"></i>dante.ali +ghieri@example.com</span> <span><i class="fa fa fa-check"></i>Poets and Writ +ers</span> </div> </div> <div class="action"></div> <div class="clear"></div> </li> <li> <div class="item-avatar"> <a href="https://intra.example.com/coworkers/francescopetr +arca/"><img src="SRCURL"></a> <span class="member-role">Sottoscrittore</span> + </div> <!-- .item-avatar --> <div class="item"> <div class="item-title"> <a href="https://intra.example.com/coworkers/francesco +ptetrarca/" class="heading"><h3>Francesco Petrarca</h3></a> + </div> <div class="item-meta"><span class="activity">active 7 + days ago, 22 hours ago</span></div> <div class="woffice-xprofile-list"> <span><i class="fa fa fa-phone"></i>02222222</span +> <span><i class="fa fa fa-mobile-phone"></i></span> <span><i class="fa fa fa-envelope-o"></i>francesco +.petrarca@example.com</span> <span><i class="fa fa fa-check"></i>Poets and Writ +ers</span> </div> </div> <div class="action"></div> <div class="clear"></div> </li> </ul>

    Output:

    $VAR1 = { 'Dante Alighieri' => { 'avatar_url' => 'SRCURL', 'fa fa fa-phone' => '011111111' 'fa fa fa-mobile-phone' => '333333333' }, 'Francesco Petrarca' => { 'avatar_url' => 'SRCURL' 'fa fa fa-phone' => '02222222', 'fa fa fa-mobile-phone' => '' } };
Re: extracting sub elements from DOM by class
by perlfan (Vicar) on Mar 27, 2021 at 15:58 UTC
    Mucking around with Web::Scraper provided an excellent environment for me to "get it", since I mostly learn by doing (and lots of head-desking due to PEBKAC). You may want to at least give that a shot, even if it is to get another perspective.

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