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