/Doc/library/htmlparser.rst
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1 2:mod:`HTMLParser` --- Simple HTML and XHTML parser 3================================================== 4 5.. module:: HTMLParser 6 :synopsis: A simple parser that can handle HTML and XHTML. 7 8.. note:: 9 10 The :mod:`HTMLParser` module has been renamed to :mod:`html.parser` in Python 11 3.0. The :term:`2to3` tool will automatically adapt imports when converting 12 your sources to 3.0. 13 14 15.. versionadded:: 2.2 16 17.. index:: 18 single: HTML 19 single: XHTML 20 21This module defines a class :class:`HTMLParser` which serves as the basis for 22parsing text files formatted in HTML (HyperText Mark-up Language) and XHTML. 23Unlike the parser in :mod:`htmllib`, this parser is not based on the SGML parser 24in :mod:`sgmllib`. 25 26 27.. class:: HTMLParser() 28 29 The :class:`HTMLParser` class is instantiated without arguments. 30 31 An :class:`HTMLParser` instance is fed HTML data and calls handler functions when tags 32 begin and end. The :class:`HTMLParser` class is meant to be overridden by the 33 user to provide a desired behavior. 34 35 Unlike the parser in :mod:`htmllib`, this parser does not check that end tags 36 match start tags or call the end-tag handler for elements which are closed 37 implicitly by closing an outer element. 38 39An exception is defined as well: 40 41 42.. exception:: HTMLParseError 43 44 Exception raised by the :class:`HTMLParser` class when it encounters an error 45 while parsing. This exception provides three attributes: :attr:`msg` is a brief 46 message explaining the error, :attr:`lineno` is the number of the line on which 47 the broken construct was detected, and :attr:`offset` is the number of 48 characters into the line at which the construct starts. 49 50:class:`HTMLParser` instances have the following methods: 51 52 53.. method:: HTMLParser.reset() 54 55 Reset the instance. Loses all unprocessed data. This is called implicitly at 56 instantiation time. 57 58 59.. method:: HTMLParser.feed(data) 60 61 Feed some text to the parser. It is processed insofar as it consists of 62 complete elements; incomplete data is buffered until more data is fed or 63 :meth:`close` is called. 64 65 66.. method:: HTMLParser.close() 67 68 Force processing of all buffered data as if it were followed by an end-of-file 69 mark. This method may be redefined by a derived class to define additional 70 processing at the end of the input, but the redefined version should always call 71 the :class:`HTMLParser` base class method :meth:`close`. 72 73 74.. method:: HTMLParser.getpos() 75 76 Return current line number and offset. 77 78 79.. method:: HTMLParser.get_starttag_text() 80 81 Return the text of the most recently opened start tag. This should not normally 82 be needed for structured processing, but may be useful in dealing with HTML "as 83 deployed" or for re-generating input with minimal changes (whitespace between 84 attributes can be preserved, etc.). 85 86 87.. method:: HTMLParser.handle_starttag(tag, attrs) 88 89 This method is called to handle the start of a tag. It is intended to be 90 overridden by a derived class; the base class implementation does nothing. 91 92 The *tag* argument is the name of the tag converted to lower case. The *attrs* 93 argument is a list of ``(name, value)`` pairs containing the attributes found 94 inside the tag's ``<>`` brackets. The *name* will be translated to lower case, 95 and quotes in the *value* have been removed, and character and entity references 96 have been replaced. For instance, for the tag ``<A 97 HREF="http://www.cwi.nl/">``, this method would be called as 98 ``handle_starttag('a', [('href', 'http://www.cwi.nl/')])``. 99 100 .. versionchanged:: 2.6 101 All entity references from :mod:`htmlentitydefs` are now replaced in the attribute 102 values. 103 104 105.. method:: HTMLParser.handle_startendtag(tag, attrs) 106 107 Similar to :meth:`handle_starttag`, but called when the parser encounters an 108 XHTML-style empty tag (``<a .../>``). This method may be overridden by 109 subclasses which require this particular lexical information; the default 110 implementation simple calls :meth:`handle_starttag` and :meth:`handle_endtag`. 111 112 113.. method:: HTMLParser.handle_endtag(tag) 114 115 This method is called to handle the end tag of an element. It is intended to be 116 overridden by a derived class; the base class implementation does nothing. The 117 *tag* argument is the name of the tag converted to lower case. 118 119 120.. method:: HTMLParser.handle_data(data) 121 122 This method is called to process arbitrary data. It is intended to be 123 overridden by a derived class; the base class implementation does nothing. 124 125 126.. method:: HTMLParser.handle_charref(name) 127 128 This method is called to process a character reference of the form ``&#ref;``. 129 It is intended to be overridden by a derived class; the base class 130 implementation does nothing. 131 132 133.. method:: HTMLParser.handle_entityref(name) 134 135 This method is called to process a general entity reference of the form 136 ``&name;`` where *name* is an general entity reference. It is intended to be 137 overridden by a derived class; the base class implementation does nothing. 138 139 140.. method:: HTMLParser.handle_comment(data) 141 142 This method is called when a comment is encountered. The *comment* argument is 143 a string containing the text between the ``--`` and ``--`` delimiters, but not 144 the delimiters themselves. For example, the comment ``<!--text-->`` will cause 145 this method to be called with the argument ``'text'``. It is intended to be 146 overridden by a derived class; the base class implementation does nothing. 147 148 149.. method:: HTMLParser.handle_decl(decl) 150 151 Method called when an SGML declaration is read by the parser. The *decl* 152 parameter will be the entire contents of the declaration inside the ``<!``...\ 153 ``>`` markup. It is intended to be overridden by a derived class; the base 154 class implementation does nothing. 155 156 157.. method:: HTMLParser.handle_pi(data) 158 159 Method called when a processing instruction is encountered. The *data* 160 parameter will contain the entire processing instruction. For example, for the 161 processing instruction ``<?proc color='red'>``, this method would be called as 162 ``handle_pi("proc color='red'")``. It is intended to be overridden by a derived 163 class; the base class implementation does nothing. 164 165 .. note:: 166 167 The :class:`HTMLParser` class uses the SGML syntactic rules for processing 168 instructions. An XHTML processing instruction using the trailing ``'?'`` will 169 cause the ``'?'`` to be included in *data*. 170 171 172.. _htmlparser-example: 173 174Example HTML Parser Application 175------------------------------- 176 177As a basic example, below is a very basic HTML parser that uses the 178:class:`HTMLParser` class to print out tags as they are encountered:: 179 180 from HTMLParser import HTMLParser 181 182 class MyHTMLParser(HTMLParser): 183 184 def handle_starttag(self, tag, attrs): 185 print "Encountered the beginning of a %s tag" % tag 186 187 def handle_endtag(self, tag): 188 print "Encountered the end of a %s tag" % tag 189