Package lxml :: Module cssselect |
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# Source Code for Module lxml.cssselect

      1  """CSS Selectors based on XPath.
      2
      3  This module supports selecting XML/HTML tags based on CSS selectors.
      4  See the `CSSSelector` class for details.
      5
      6  This is a thin wrapper around cssselect 0.7 or later.
      7  """
      8
      9  from __future__ import absolute_import
     10
     11  from . import etree
     12  try:
     13      import cssselect as external_cssselect
     14  except ImportError:
     15      raise ImportError(
     16          'cssselect does not seem to be installed. '
     17          'See http://packages.python.org/cssselect/')
     18
     19
     20  SelectorSyntaxError = external_cssselect.SelectorSyntaxError
     21  ExpressionError = external_cssselect.ExpressionError
     22  SelectorError = external_cssselect.SelectorError
     23
     24
     25  __all__ = ['SelectorSyntaxError', 'ExpressionError', 'SelectorError',
     26             'CSSSelector']
     27
     28
     29 -class LxmlTranslator(external_cssselect.GenericTranslator):
     30      """
     31      A custom CSS selector to XPath translator with lxml-specific extensions.
     32      """
     33 -    def xpath_contains_function(self, xpath, function):
     34          # Defined there, removed in later drafts:
     35          # http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#content-selectors
     36          if function.argument_types() not in (['STRING'], ['IDENT']):
     37              raise ExpressionError(
     38                  "Expected a single string or ident for :contains(), got %r"
     39                  % function.arguments)
     40          value = function.arguments[0].value
     41          return xpath.add_condition(
     42              'contains(__lxml_internal_css:lower-case(string(.)), %s)'
     43              % self.xpath_literal(value.lower()))
     44
     45
     46 -class LxmlHTMLTranslator(LxmlTranslator, external_cssselect.HTMLTranslator):
     47      """
     48      lxml extensions + HTML support.
     49      """
     50
     51
     52 -def _make_lower_case(context, s):
     53      return s.lower()
     54
     55  ns = etree.FunctionNamespace('http://codespeak.net/lxml/css/')
     56  ns.prefix = '__lxml_internal_css'
     57  ns['lower-case'] = _make_lower_case
     58
     59
     60 -class CSSSelector(etree.XPath):
     61      """A CSS selector.
     62
     63      Usage::
     64
     65          >>> from lxml import etree, cssselect
     66          >>> select = cssselect.CSSSelector("a tag > child")
     67
     68          >>> root = etree.XML("<a><b><c/><tag><child>TEXT</child></tag></b></a>")
     69          >>> [ el.tag for el in select(root) ]
     70          ['child']
     71
     72      To use CSS namespaces, you need to pass a prefix-to-namespace
     73      mapping as ``namespaces`` keyword argument::
     74
     75          >>> rdfns = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
     76          >>> select_ns = cssselect.CSSSelector('root > rdf|Description',
     77          ...                                   namespaces={'rdf': rdfns})
     78
     79          >>> rdf = etree.XML((
     80          ...     '<root xmlns:rdf="%s">'
     81          ...       '<rdf:Description>blah</rdf:Description>'
     82          ...     '</root>') % rdfns)
     83          >>> [(el.tag, el.text) for el in select_ns(rdf)]
     84          [('{http://www.w3.org/1999/02/22-rdf-syntax-ns#}Description', 'blah')]
     85
     86      """
     87 -    def __init__(self, css, namespaces=None, translator='xml'):
     88          if translator == 'xml':
     89              translator = LxmlTranslator()
     90          elif translator == 'html':
     91              translator = LxmlHTMLTranslator()
     92          elif translator == 'xhtml':
     93              translator = LxmlHTMLTranslator(xhtml=True)
     94          path = translator.css_to_xpath(css)
     95          etree.XPath.__init__(self, path, namespaces=namespaces)
     96          self.css = css
     97
     98 -    def __repr__(self):
     99          return '<%s %s for %r>' % (
    100              self.__class__.__name__,
    101              hex(abs(id(self)))[2:],
    102              self.css)
    103