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  import sys
     10  from lxml import etree
     11
     12  ## Work-around the lack of absolute import in Python 2.4
     13  #from __future__ import absolute_import
     14  #from cssselect import ...
     15  try:
     16      external_cssselect = __import__('cssselect')
     17  except ImportError:
     18      raise ImportError('cssselect seems not to be installed. '
     19                        'See http://packages.python.org/cssselect/')
     20
     21  SelectorSyntaxError = external_cssselect.SelectorSyntaxError
     22  ExpressionError = external_cssselect.ExpressionError
     23  SelectorError = external_cssselect.SelectorError
     24
     25
     26  __all__ = ['SelectorSyntaxError', 'ExpressionError', 'SelectorError',
     27             'CSSSelector']
     28
     29
     30 -class LxmlTranslator(external_cssselect.GenericTranslator):
     31      """
     32      A custom CSS selector to XPath translator with lxml-specific extensions.
     33      """
     34 -    def xpath_contains_function(self, xpath, function):
     35          # Defined there, removed in later drafts:
     36          # http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#content-selectors
     37          if function.argument_types() not in (['STRING'], ['IDENT']):
     38              raise ExpressionError(
     39                  "Expected a single string or ident for :contains(), got %r"
     40                  % function.arguments)
     41          value = function.arguments[0].value
     42          return xpath.add_condition(
     43              'contains(__lxml_internal_css:lower-case(string(.)), %s)'
     44              % self.xpath_literal(value.lower()))
     45
     46
     47 -class LxmlHTMLTranslator(LxmlTranslator, external_cssselect.HTMLTranslator):
     48      """
     49      lxml extensions + HTML support.
     50      """
     51
     52
     53 -def _make_lower_case(context, s):
     54      return s.lower()
     55
     56  ns = etree.FunctionNamespace('http://codespeak.net/lxml/css/')
     57  ns.prefix = '__lxml_internal_css'
     58  ns['lower-case'] = _make_lower_case
     59
     60
     61 -class CSSSelector(etree.XPath):
     62      """A CSS selector.
     63
     64      Usage::
     65
     66          >>> from lxml import etree, cssselect
     67          >>> select = cssselect.CSSSelector("a tag > child")
     68
     69          >>> root = etree.XML("<a><b><c/><tag><child>TEXT</child></tag></b></a>")
     70          >>> [ el.tag for el in select(root) ]
     71          ['child']
     72
     73      To use CSS namespaces, you need to pass a prefix-to-namespace
     74      mapping as ``namespaces`` keyword argument::
     75
     76          >>> rdfns = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
     77          >>> select_ns = cssselect.CSSSelector('root > rdf|Description',
     78          ...                                   namespaces={'rdf': rdfns})
     79
     80          >>> rdf = etree.XML((
     81          ...     '<root xmlns:rdf="%s">'
     82          ...       '<rdf:Description>blah</rdf:Description>'
     83          ...     '</root>') % rdfns)
     84          >>> [(el.tag, el.text) for el in select_ns(rdf)]
     85          [('{http://www.w3.org/1999/02/22-rdf-syntax-ns#}Description', 'blah')]
     86
     87      """
     88 -    def __init__(self, css, namespaces=None, translator='xml'):
     89          if translator == 'xml':
     90              translator = LxmlTranslator()
     91          elif translator == 'html':
     92              translator = LxmlHTMLTranslator()
     93          elif translator == 'xhtml':
     94              translator = LxmlHTMLTranslator(xhtml=True)
     95          path = translator.css_to_xpath(css)
     96          etree.XPath.__init__(self, path, namespaces=namespaces)
     97          self.css = css
     98
     99 -    def __repr__(self):
    100          return '<%s %s for %r>' % (
    101              self.__class__.__name__,
    102              hex(abs(id(self)))[2:],
    103              self.css)
    104