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103 lines
3.3 KiB
103 lines
3.3 KiB
2 years ago
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"""CSS Selectors based on XPath.
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This module supports selecting XML/HTML tags based on CSS selectors.
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See the `CSSSelector` class for details.
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This is a thin wrapper around cssselect 0.7 or later.
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"""
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from __future__ import absolute_import
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from . import etree
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try:
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import cssselect as external_cssselect
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except ImportError:
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raise ImportError(
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'cssselect does not seem to be installed. '
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'See http://packages.python.org/cssselect/')
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SelectorSyntaxError = external_cssselect.SelectorSyntaxError
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ExpressionError = external_cssselect.ExpressionError
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SelectorError = external_cssselect.SelectorError
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__all__ = ['SelectorSyntaxError', 'ExpressionError', 'SelectorError',
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'CSSSelector']
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class LxmlTranslator(external_cssselect.GenericTranslator):
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"""
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A custom CSS selector to XPath translator with lxml-specific extensions.
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"""
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def xpath_contains_function(self, xpath, function):
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# Defined there, removed in later drafts:
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# http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#content-selectors
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if function.argument_types() not in (['STRING'], ['IDENT']):
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raise ExpressionError(
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"Expected a single string or ident for :contains(), got %r"
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% function.arguments)
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value = function.arguments[0].value
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return xpath.add_condition(
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'contains(__lxml_internal_css:lower-case(string(.)), %s)'
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% self.xpath_literal(value.lower()))
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class LxmlHTMLTranslator(LxmlTranslator, external_cssselect.HTMLTranslator):
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"""
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lxml extensions + HTML support.
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"""
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def _make_lower_case(context, s):
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return s.lower()
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ns = etree.FunctionNamespace('http://codespeak.net/lxml/css/')
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ns.prefix = '__lxml_internal_css'
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ns['lower-case'] = _make_lower_case
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class CSSSelector(etree.XPath):
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"""A CSS selector.
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Usage::
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>>> from lxml import etree, cssselect
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>>> select = cssselect.CSSSelector("a tag > child")
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>>> root = etree.XML("<a><b><c/><tag><child>TEXT</child></tag></b></a>")
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>>> [ el.tag for el in select(root) ]
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['child']
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To use CSS namespaces, you need to pass a prefix-to-namespace
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mapping as ``namespaces`` keyword argument::
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>>> rdfns = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
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>>> select_ns = cssselect.CSSSelector('root > rdf|Description',
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... namespaces={'rdf': rdfns})
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>>> rdf = etree.XML((
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... '<root xmlns:rdf="%s">'
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... '<rdf:Description>blah</rdf:Description>'
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... '</root>') % rdfns)
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>>> [(el.tag, el.text) for el in select_ns(rdf)]
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[('{http://www.w3.org/1999/02/22-rdf-syntax-ns#}Description', 'blah')]
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"""
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def __init__(self, css, namespaces=None, translator='xml'):
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if translator == 'xml':
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translator = LxmlTranslator()
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elif translator == 'html':
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translator = LxmlHTMLTranslator()
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elif translator == 'xhtml':
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translator = LxmlHTMLTranslator(xhtml=True)
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path = translator.css_to_xpath(css)
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etree.XPath.__init__(self, path, namespaces=namespaces)
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self.css = css
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def __repr__(self):
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return '<%s %s for %r>' % (
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self.__class__.__name__,
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hex(abs(id(self)))[2:],
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self.css)
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