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