[lxml-dev] CSS and lxml

[Frederik Elwert]

Hello!

I am currently looking into the possibilities to work with CSS in lxml
or Python in general. I hope it's not too off-topic, but since it's
related to lxml, I thought I might post it here.

The specific use case I have in mind would take an element and look for
all applying CSS rules. Let's say we have a style element:

<style type="text/css">
p {
  font-size: 16pt;
}
p.strong {
  font-weight: bold;
}
</style>

and in the tree, there are two elements:

<p style="color:red;">Some text</p>
<p class="strong">Some other text</p>

Then I'd like to get something like

>>> el1.getstyle()
{'font-size': '16pt', 'color': 'red'}

for the first element and

>>> el2.getstyle()
{'font-size': '16pt', 'font-weight': 'bold'}
for the second one.

I know that this is currently not possible. The only true CSS library
for Python that I found were cssutils <http://cthedot.de/cssutils/>.
They have quite sophisticated support for CSS parsing, but I think the
library itself is quite DOM-centric and so it's not very pythonic /
doesn't fit well to lxml. But more important, it has no real XML
bindings. So it's possible to query stylesheets to get properties that
match a selector:

>>> stylesheet.props('p.strong')
{'font-size': '16pt', 'font-weight': 'bold'}

but not to query true elements to get the applying properties.

On the other hand, lxml now has cssselect, which works the other way
around: It takes a selector and returns all the elements that match that
selector.

>>> sel = CSSSelector('p.strong')
>>> [e.text for e in sel(tree)]
['Some other text']

So I just wanted to ask if somebody already had thought about this, or
if somebody has any ideas in which direction to head to solve this
problem.

Maybe one could write a module, that combines cssutils and
lxml.cssselect to match css style properties and actual elements. But
maybe a completely different approach would be needed.

Regards,
Frederik