19.2. html.parser — Simple HTML and XHTML parser

Source code: Lib/html/parser.py

This module defines a class HTMLParser which serves as the basis for parsing text files formatted in HTML (HyperText Mark-up Language) and XHTML.

class html.parser.HTMLParser(strict=True)

Create a parser instance. If strict is True (the default), invalid html results in HTMLParseError exceptions [1]. If strict is False, the parser uses heuristics to make a best guess at the intention of any invalid html it encounters, similar to the way most browsers do.

An HTMLParser instance is fed HTML data and calls handler functions when tags begin and end. The HTMLParser class is meant to be overridden by the user to provide a desired behavior.

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.

Changed in version 3.2: strict keyword added

An exception is defined as well:

exception html.parser.HTMLParseError

Exception raised by the HTMLParser class when it encounters an error while parsing. This exception provides three attributes: msg is a brief message explaining the error, lineno is the number of the line on which the broken construct was detected, and offset is the number of characters into the line at which the construct starts.

HTMLParser instances have the following methods:

HTMLParser.reset()

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

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 close() is called.

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 HTMLParser base class method close().

HTMLParser.getpos()

Return current line number and offset.

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.).

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/')]).

All entity references from html.entities are replaced in the attribute values.

HTMLParser.handle_startendtag(tag, attrs)

Similar to 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 handle_starttag() and handle_endtag().

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.

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.

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.

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.

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.

HTMLParser.handle_decl(decl)

Method called when an SGML doctype 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.

HTMLParser.unknown_decl(data)

Method called when an unrecognized SGML declaration is read by the parser. The data parameter will be the entire contents of the declaration inside the <!...> markup. It is sometimes useful to be overridden by a derived class; the base class implementation raises an HTMLParseError.

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 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.

>>> from html.parser import HTMLParser
>>>
>>> class MyHTMLParser(HTMLParser):
...     def handle_starttag(self, tag, attrs):
...         print("Encountered a {} start tag".format(tag))
...     def handle_endtag(self, tag):
...         print("Encountered a {} end tag".format(tag))
...
>>> page = """<html><h1>Title</h1><p>I'm a paragraph!</p></html>"""
>>>
>>> myparser = MyHTMLParser()
>>> myparser.feed(page)
Encountered a html start tag
Encountered a h1 start tag
Encountered a h1 end tag
Encountered a p start tag
Encountered a p end tag
Encountered a html end tag