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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 . 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 https://pypi.org/project/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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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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super().__init__(path, namespaces=namespaces) |
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self.css = css |
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def __repr__(self): |
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return '<%s %x for %r>' % ( |
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self.__class__.__name__, |
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abs(id(self)), |
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self.css) |
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