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"""CSS Selectors based on XPath.
This module supports selecting XML/HTML tags based on CSS selectors.
See the `CSSSelector` class for details.
This is a thin wrapper around cssselect 0.7 or later.
"""
from __future__ import absolute_import
from . import etree
try:
import cssselect as external_cssselect
except ImportError:
raise ImportError(
'cssselect does not seem to be installed. '
'See https://pypi.org/project/cssselect/')
SelectorSyntaxError = external_cssselect.SelectorSyntaxError
ExpressionError = external_cssselect.ExpressionError
SelectorError = external_cssselect.SelectorError
__all__ = ['SelectorSyntaxError', 'ExpressionError', 'SelectorError',
'CSSSelector']
class LxmlTranslator(external_cssselect.GenericTranslator):
"""
A custom CSS selector to XPath translator with lxml-specific extensions.
"""
def xpath_contains_function(self, xpath, function):
# Defined there, removed in later drafts:
# http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#content-selectors
if function.argument_types() not in (['STRING'], ['IDENT']):
raise ExpressionError(
"Expected a single string or ident for :contains(), got %r"
% function.arguments)
value = function.arguments[0].value
return xpath.add_condition(
'contains(__lxml_internal_css:lower-case(string(.)), %s)'
% self.xpath_literal(value.lower()))
class LxmlHTMLTranslator(LxmlTranslator, external_cssselect.HTMLTranslator):
"""
lxml extensions + HTML support.
"""
def _make_lower_case(context, s):
return s.lower()
ns = etree.FunctionNamespace('http://codespeak.net/lxml/css/')
ns.prefix = '__lxml_internal_css'
ns['lower-case'] = _make_lower_case
class CSSSelector(etree.XPath):
"""A CSS selector.
Usage::
>>> from lxml import etree, cssselect
>>> select = cssselect.CSSSelector("a tag > child")
>>> root = etree.XML("<a><b><c/><tag><child>TEXT</child></tag></b></a>")
>>> [ el.tag for el in select(root) ]
['child']
To use CSS namespaces, you need to pass a prefix-to-namespace
mapping as ``namespaces`` keyword argument::
>>> rdfns = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
>>> select_ns = cssselect.CSSSelector('root > rdf|Description',
... namespaces={'rdf': rdfns})
>>> rdf = etree.XML((
... '<root xmlns:rdf="%s">'
... '<rdf:Description>blah</rdf:Description>'
... '</root>') % rdfns)
>>> [(el.tag, el.text) for el in select_ns(rdf)]
[('{http://www.w3.org/1999/02/22-rdf-syntax-ns#}Description', 'blah')]
"""
def __init__(self, css, namespaces=None, translator='xml'):
if translator == 'xml':
translator = LxmlTranslator()
elif translator == 'html':
translator = LxmlHTMLTranslator()
elif translator == 'xhtml':
translator = LxmlHTMLTranslator(xhtml=True)
path = translator.css_to_xpath(css)
super(CSSSelector, self).__init__(path, namespaces=namespaces)
self.css = css
def __repr__(self):
return '<%s %x for %r>' % (
self.__class__.__name__,
abs(id(self)),
self.css)
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