Parse_Html
html.parser — Simple HTML and XHTML parser — Python …
Source code: Lib/html/
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 (*, convert_charrefs=True)¶
Create a parser instance able to parse invalid markup.
If convert_charrefs is True (the default), all character
references (except the ones in script/style elements) are
automatically converted to the corresponding Unicode characters.
An HTMLParser instance is fed HTML data and calls handler methods
when start tags, end tags, text, comments, and other markup elements are
encountered. The user should subclass HTMLParser and override its
methods to implement the 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. 4: convert_charrefs keyword argument added.
Changed in version 3. 5: The default value for argument convert_charrefs is now True.
Example HTML Parser Application¶
As a basic example, below is a simple HTML parser that uses the
HTMLParser class to print out start tags, end tags, and data
as they are encountered:
from import HTMLParser
class MyHTMLParser(HTMLParser):
def handle_starttag(self, tag, attrs):
print(“Encountered a start tag:”, tag)
def handle_endtag(self, tag):
print(“Encountered an end tag:”, tag)
def handle_data(self, data):
print(“Encountered some data:”, data)
parser = MyHTMLParser()
(‘
‘
Parse me!
‘)
The output will then be:
Encountered a start tag: html
Encountered a start tag: head
Encountered a start tag: title
Encountered some data: Test
Encountered an end tag: title
Encountered an end tag: head
Encountered a start tag: body
Encountered a start tag: h1
Encountered some data: Parse me!
Encountered an end tag: h1
Encountered an end tag: body
Encountered an end tag: html
HTMLParser Methods¶
HTMLParser instances have the following methods:
(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. data must be str.
()¶
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().
Reset the instance. Loses all unprocessed data. This is called implicitly at
instantiation time.
Return current line number and offset.
t_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. ).
The following methods are called when data or markup elements are encountered
and they are meant to be overridden in a subclass. The base class
implementations do nothing (except for handle_startendtag()):
HTMLParser. handle_starttag(tag, attrs)¶
This method is called to handle the start of a tag (e. g.
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 ‘)
Decl: DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4. 01//EN” ”
Parsing an element with a few attributes and a title:
>>> (‘
Start tag: img
attr: (‘src’, ”)
attr: (‘alt’, ‘The Python logo’)
>>>
>>> (‘
Python
‘)
Start tag: h1
Data: Python
End tag: h1
The content of script and style elements is returned as is, without
further parsing:
>>> (‘
‘)
Start tag: style
attr: (‘type’, ‘text/css’)
Data: #python { color: green}
End tag: style
>>> (‘‘)
Start tag: script
attr: (‘type’, ‘text/javascript’)
Data: alert(“hello! “);
End tag: script
Parsing comments:
>>> (‘‘… ‘IE-specific content‘)
Comment: a comment
Comment: [if IE 9]>IE-specific content‘):
>>> (‘>>>’)
Named ent: >
Num ent: >
Feeding incomplete chunks to feed() works, but
handle_data() might be called more than once
(unless convert_charrefs is set to True):
>>> for chunk in [‘
Start tag: span
Data: buff
Data: ered
Data: text
End tag: span
Parsing invalid HTML (e. unquoted attributes) also works:
>>> (‘
Start tag: p
Start tag: a
attr: (‘class’, ‘link’)
attr: (‘href’, ‘#main’)
Data: tag soup
End tag: p
End tag: a
Parse – MDN Web Docs Glossary: Definitions of Web-related …
Parsing means analyzing and converting a program into an internal format that a runtime environment can actually run, for example the JavaScript engine inside browsers.
The browser parses HTML into a DOM tree. HTML parsing involves tokenization and tree construction. HTML tokens include start and end tags, as well as attribute names and values. If the document is well-formed, parsing it is straightforward and faster. The parser parses tokenized input into the document, building up the document tree.
When the HTML parser finds non-blocking resources, such as an image, the browser will request those resources and continue parsing. Parsing can continue when a CSS file is encountered, but