在 perl 中使用 web::scraper 提取特定信息

Question

我是网络抓取的新手。我想知道是否可以在 perl 中使用web::scraper 提取特定信息。例如，我的 html 如下所示（我从 URL 中提取了部分 html）：

 <table class="reference">
     <tr>
     <th width="23%" align="left">Property</th>
     <th width="71%" align="left">Description</th>
     <th style="text-align:center;">DOM</th>
     </tr>
     <tr>
        <td><a href="prop_node_attributes.asp">attributes</a></td>
        <td>Returns a collection of a node's attributes</td>
        <td style="text-align:center;">1</td>
     </tr>

     <tr>
        <td><a href="prop_node_baseuri.asp">baseURI</a></td>
        <td>Returns the absolute base URI of a node</td>
        <td style="text-align:center;">3</td>
     </tr>
     <tr>
        <td><a href="prop_node_childnodes.asp">childNodes</a></td>
        <td>Returns a NodeList of child nodes for a node</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_firstchild.asp">firstChild</a></td>
        <td>Returns the first child of a node</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_lastchild.asp">lastChild</a></td>
        <td>Returns the last child of a node</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_localname.asp">localName</a></td>
        <td>Returns the local part of the name of a node</td>
        <td style="text-align:center;">2</td>
     </tr>
     <tr>
        <td><a href="prop_node_namespaceuri.asp">namespaceURI</a></td>
        <td>Returns the namespace URI of a node</td>
        <td style="text-align:center;">2</td>
     </tr>
     <tr>
        <td><a href="prop_node_nextsibling.asp">nextSibling</a></td>
        <td>Returns the next node at the same node tree level</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_nodename.asp">nodeName</a></td>
        <td>Returns the name of a node, depending on its type</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_nodetype.asp">nodeType</a></td>
        <td>Returns the type of a node</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_nodevalue.asp">nodeValue</a></td>
        <td>Sets or returns the value of a node, depending on its 
        type</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_ownerdocument.asp">ownerDocument</a></td>
        <td>Returns the root element (document object) for a node</td>
        <td style="text-align:center;">2</td>
     </tr>
     <tr>
        <td><a href="prop_node_parentnode.asp">parentNode</a></td>
        <td>Returns the parent node of a node</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_prefix.asp">prefix</a></td>
        <td>Sets or returns the namespace prefix of a node</td>
        <td style="text-align:center;">2</td>
     </tr>
     <tr>
        <td><a href="prop_node_previoussibling.asp">previousSibling</a></td>
        <td>Returns the previous node at the same node tree level</td>
        <td style="text-align:center;">1</td>
     </tr>
     <tr>
        <td><a href="prop_node_textcontent.asp">textContent</a></td>
        <td>Sets or returns the textual content of a node and its 
        descendants</td>
        <td style="text-align:center;">3</td>
     </tr>
     </table>

所以我的 perl 代码是这样的：

#!/usr/bin/perl
use warnings;
use strict;
use URI;
use Web::Scraper;

# website to scrape
my $urlToScrape = "http://www.w3schools.com/jsref/dom_obj_node.asp";

my $rennersdata = scraper {
 process "table.reference > tr > td", 'landrenner[]' => 'TEXT';
 };

my $res = $teamsdata->scrape(URI->new($urlToScrape));
for my $i (0 .. $#{$res->{landrenner}}) {

print $res->{landrenner}[$i];
print "\n";
}

当我运行上面的代码时，我得到了td 标签内的所有文本。 i-e 对于$i=0，输出为：

attributes
Returns a collection of a node's attributes
1

是不是只能得到输出：

Returns a collection of a node's attributes

为了获得上述输出，我必须进行哪些更改？

Answer 1

通过调整 CSS 选择器告诉它你只想要第二个 td；而不是"table.reference > tr > td" 做"table.reference > tr > td:nth-of-type(2)"