:mod:`HTMLParser` --- Simple HTML and XHTML parser

==================================================

.. module:: HTMLParser

   :synopsis: A simple parser that can handle HTML and XHTML.

.. note::

   The :mod:`HTMLParser` module has been renamed to :mod:`html.parser` in Python

   3.0.  The :term:`2to3` tool will automatically adapt imports when converting

   your sources to 3.0.

.. versionadded:: 2.2

.. index::

   single: HTML

   single: XHTML

This module defines a class :class:`HTMLParser` which serves as the basis for

parsing text files formatted in HTML (HyperText Mark-up Language) and XHTML.

Unlike the parser in :mod:`htmllib`, this parser is not based on the SGML parser

in :mod:`sgmllib`.

.. class:: HTMLParser()

   The :class:`HTMLParser` class is instantiated without arguments.

   An :class:`HTMLParser` instance is fed HTML data and calls handler functions when tags

   begin and end.  The :class:`HTMLParser` class is meant to be overridden by the

   user to provide a desired behavior.

   Unlike the parser in :mod:`htmllib`, this parser does not check that end tags

   match start tags or call the end-tag handler for elements which are closed

   implicitly by closing an outer element.

An exception is defined as well:

.. exception:: HTMLParseError

   Exception raised by the :class:`HTMLParser` class when it encounters an error

   while parsing.  This exception provides three attributes: :attr:`msg` is a brief

   message explaining the error, :attr:`lineno` is the number of the line on which

   the broken construct was detected, and :attr:`offset` is the number of

   characters into the line at which the construct starts.

:class:`HTMLParser` instances have the following methods:

.. method:: HTMLParser.reset()

   Reset the instance.  Loses all unprocessed data.  This is called implicitly at

   instantiation time.

.. method:: HTMLParser.feed(data)

   Feed some text to the parser.  It is processed insofar as it consists of

   complete elements; incomplete data is buffered until more data is fed or

   :meth:`close` is called.

.. method:: HTMLParser.close()

   Force processing of all buffered data as if it were followed by an end-of-file

   mark.  This method may be redefined by a derived class to define additional

   processing at the end of the input, but the redefined version should always call

   the :class:`HTMLParser` base class method :meth:`close`.

.. method:: HTMLParser.getpos()

   Return current line number and offset.

.. method:: HTMLParser.get_starttag_text()

   Return the text of the most recently opened start tag.  This should not normally

   be needed for structured processing, but may be useful in dealing with HTML "as

   deployed" or for re-generating input with minimal changes (whitespace between

   attributes can be preserved, etc.).

.. method:: HTMLParser.handle_starttag(tag, attrs)

   This method is called to handle the start of a tag.  It is intended to be

   overridden by a derived class; the base class implementation does nothing.

   The *tag* argument is the name of the tag converted to lower case. The *attrs*

   argument is a list of ``(name, value)`` pairs containing the attributes found

   inside the tag's ``<>`` brackets.  The *name* will be translated to lower case,

   and quotes in the *value* have been removed, and character and entity references

   have been replaced.  For instance, for the tag ``<A

   HREF="http://www.cwi.nl/">``, this method would be called as

   ``handle_starttag('a', [('href', 'http://www.cwi.nl/')])``.

   .. versionchanged:: 2.6

      All entity references from :mod:`htmlentitydefs` are now replaced in the attribute

      values.

.. method:: HTMLParser.handle_startendtag(tag, attrs)

   Similar to :meth:`handle_starttag`, but called when the parser encounters an

   XHTML-style empty tag (``<a .../>``).  This method may be overridden by

   subclasses which require this particular lexical information; the default

   implementation simple calls :meth:`handle_starttag` and :meth:`handle_endtag`.

.. method:: HTMLParser.handle_endtag(tag)

   This method is called to handle the end tag of an element.  It is intended to be

   overridden by a derived class; the base class implementation does nothing.  The

   *tag* argument is the name of the tag converted to lower case.

.. method:: HTMLParser.handle_data(data)

   This method is called to process arbitrary data.  It is intended to be

   overridden by a derived class; the base class implementation does nothing.

.. method:: HTMLParser.handle_charref(name)

   This method is called to process a character reference of the form ``&#ref;``.

   It is intended to be overridden by a derived class; the base class

   implementation does nothing.

.. method:: HTMLParser.handle_entityref(name)

   This method is called to process a general entity reference of the form

   ``&name;`` where *name* is an general entity reference.  It is intended to be

   overridden by a derived class; the base class implementation does nothing.

.. method:: HTMLParser.handle_comment(data)

   This method is called when a comment is encountered.  The *comment* argument is

   a string containing the text between the ``--`` and ``--`` delimiters, but not

   the delimiters themselves.  For example, the comment ``<!--text-->`` will cause

   this method to be called with the argument ``'text'``.  It is intended to be

   overridden by a derived class; the base class implementation does nothing.

.. method:: HTMLParser.handle_decl(decl)

   Method called when an SGML declaration is read by the parser.  The *decl*

   parameter will be the entire contents of the declaration inside the ``<!``...\

   ``>`` markup.  It is intended to be overridden by a derived class; the base

   class implementation does nothing.

.. method:: HTMLParser.handle_pi(data)

   Method called when a processing instruction is encountered.  The *data*

   parameter will contain the entire processing instruction. For example, for the

   processing instruction ``<?proc color='red'>``, this method would be called as

   ``handle_pi("proc color='red'")``.  It is intended to be overridden by a derived

   class; the base class implementation does nothing.

   .. note::

      The :class:`HTMLParser` class uses the SGML syntactic rules for processing

      instructions.  An XHTML processing instruction using the trailing ``'?'`` will

      cause the ``'?'`` to be included in *data*.

.. _htmlparser-example:

Example HTML Parser Application

-------------------------------

As a basic example, below is a very basic HTML parser that uses the

:class:`HTMLParser` class to print out tags as they are encountered::

   from HTMLParser import HTMLParser

   class MyHTMLParser(HTMLParser):

       def handle_starttag(self, tag, attrs):

           print "Encountered the beginning of a %s tag" % tag

       def handle_endtag(self, tag):

           print "Encountered the end of a %s tag" % tag