Question

I am brand new to python, and I need some help with the syntax for finding and iterating through html tags using lxml. Here are the use-cases I am dealing with:

HTML file is fairly well formed (but not perfect). Has multiple tables on screen, one containing a set of search results, and one each for a header and footer. Each result row contains a link for the search result detail.

1. I need to find the middle table with the search result rows (this one I was able to figure out):

       self.mySearchTables = self.mySearchTree.findall('.//table')     self.myResultRows = self.mySearchTables[1].findall('.//tr') 

2. I need to find the links contained in this table (this is where I’m getting stuck):

       for searchRow in self.myResultRows:         searchLink = patentRow.findall('.//a') 

   It doesn’t seem to actually locate the link elements.

3. I need the plain text of the link. I imagine it would be something like searchLink.text if I actually got the link elements in the first place.

Finally, in the actual API reference for lxml, I wasn’t able to find information on the find and the findall calls. I gleaned these from bits of code I found on google. Am I missing something about how to effectively find and iterate over HTML tags using lxml?

Answer 1

Okay, first, in regards to parsing the HTML: if you follow the recommendation of zweiterlinde and S.Lott at least use the version of beautifulsoup included with lxml. That way you will also reap the benefit of a nice xpath or css selector interface.

However, I personally prefer Ian Bicking’s HTML parser included in lxml.

Secondly, .find() and .findall() come from lxml trying to be compatible with ElementTree, and those two methods are described in XPath Support in ElementTree.

Those two functions are fairly easy to use but they are very limited XPath. I recommend trying to use either the full lxml xpath() method or, if you are already familiar with CSS, using the cssselect() method.

Here are some examples, with an HTML string parsed like this:

from lxml.html import fromstring mySearchTree = fromstring(your_input_string) 

Using the css selector class your program would roughly look something like this:

# Find all 'a' elements inside 'tr' table rows with css selector for a in mySearchTree.cssselect('tr a'):     print 'found '%s' link to href '%s'' % (a.text, a.get('href')) 

The equivalent using xpath method would be:

# Find all 'a' elements inside 'tr' table rows with xpath for a in mySearchTree.xpath('.//tr/*/a'):     print 'found '%s' link to href '%s'' % (a.text, a.get('href'))