html.parser
— 简单 HTML 和 XHTML 剖析器
¶
源代码： Lib/html/parser.py
此模块定义的类
HTMLParser
其充当剖析 HTML (超文本标记语言) 和 XHTML 格式文本文件的基础。
html.parser.
HTMLParser
(
*
,
convert_charrefs=True
)
¶
创建能够剖析无效标记的剖析器实例。
若
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.
3.4 版改变： convert_charrefs keyword argument added.
3.5 版改变：
The default value for argument
convert_charrefs
现为
True
.
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 html.parser 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()
parser.feed('<html><head><title>Test</title></head>'
'<body><h1>Parse me!</h1></body></html>')
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
方法
¶
HTMLParser
实例具有下列方法：
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()
被调用。
data
必须是
str
.
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.
reset
(
)
¶
Reset the instance. Loses all unprocessed data. This is called implicitly at instantiation time.
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.).
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.
<div
id="main">
).
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="https://www.cwi.nl/">
, this method would be called as
handle_starttag('a',
[('href',
'https://www.cwi.nl/')])
.
All entity references from
html.entities
are replaced in the attribute values.
HTMLParser.
handle_endtag
(
tag
)
¶
This method is called to handle the end tag of an element (e.g.
</div>
).
tag argument is the name of the tag converted to lower case.
HTMLParser.
handle_startendtag
(
tag
,
attrs
)
¶
类似
handle_starttag()
, but called when the parser encounters an XHTML-style empty tag (
<img
...
/>
). This method may be overridden by subclasses which require this particular lexical information; the default implementation simply calls
handle_starttag()
and
handle_endtag()
.
HTMLParser.
handle_data
(
data
)
¶
This method is called to process arbitrary data (e.g. text nodes and the content of
<script>...</script>
and
<style>...</style>
).
HTMLParser.
handle_entityref
(
name
)
¶
This method is called to process a named character reference of the form
&name;
(e.g.
>
), where
name
is a general entity reference (e.g.
'gt'
). This method is never called if
convert_charrefs
is
True
.
HTMLParser.
handle_charref
(
name
)
¶
This method is called to process decimal and hexadecimal numeric character references of the form
&#NNN;
and
&#xNNN;
. For example, the decimal equivalent for
>
is
>
, whereas the hexadecimal is
>
; in this case the method will receive
'62'
or
'x3E'
. This method is never called if
convert_charrefs
is
True
.
HTMLParser.
handle_comment
(
data
)
¶
This method is called when a comment is encountered (e.g.
<!--comment-->
).
For example, the comment
<!--
comment
-->
will cause this method to be called with the argument
'
comment
'
.
The content of Internet Explorer conditional comments (condcoms) will also be sent to this method, so, for
<!--[if
IE
9]>IE9-specific
content<![endif]-->
, this method will receive
'[if
IE
9]>IE9-specific
content<![endif]'
.
HTMLParser.
handle_decl
(
decl
)
¶
This method is called to handle an HTML doctype declaration (e.g.
<!DOCTYPE
html>
).
decl
parameter will be the entire contents of the declaration inside the
<!...>
markup (e.g.
'DOCTYPE
html'
).
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.
注意
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.
unknown_decl
(
data
)
¶
This method is called when an unrecognized declaration is read by the parser.
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 does nothing.
The following class implements a parser that will be used to illustrate more examples:
from html.parser import HTMLParser
from html.entities import name2codepoint
class MyHTMLParser(HTMLParser):
def handle_starttag(self, tag, attrs):
print("Start tag:", tag)
for attr in attrs:
print(" attr:", attr)
def handle_endtag(self, tag):
print("End tag :", tag)
def handle_data(self, data):
print("Data :", data)
def handle_comment(self, data):
print("Comment :", data)
def handle_entityref(self, name):
c = chr(name2codepoint[name])
print("Named ent:", c)
def handle_charref(self, name):
if name.startswith('x'):
c = chr(int(name[1:], 16))
else:
c = chr(int(name))
print("Num ent :", c)
def handle_decl(self, data):
print("Decl :", data)
parser = MyHTMLParser()
剖析 doctype：
>>> parser.feed('<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" '
... '"http://www.w3.org/TR/html4/strict.dtd">')
Decl : DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"
Parsing an element with a few attributes and a title:
>>> parser.feed('<img src="python-logo.png" alt="The Python logo">')
Start tag: img
attr: ('src', 'python-logo.png')
attr: ('alt', 'The Python logo')
>>>
>>> parser.feed('<h1>Python</h1>')
Start tag: h1
Data : Python
End tag : h1
The content of
script
and
style
elements is returned as is, without further parsing:
>>> parser.feed('<style type="text/css">#python { color: green }</style>')
Start tag: style
attr: ('type', 'text/css')
Data : #python { color: green }
End tag : style
>>> parser.feed('<script type="text/javascript">'
... 'alert("<strong>hello!</strong>");</script>')
Start tag: script
attr: ('type', 'text/javascript')
Data : alert("<strong>hello!</strong>");
End tag : script
剖析注释：
>>> parser.feed('<!-- a comment -->'
... '<!--[if IE 9]>IE-specific content<![endif]-->')
Comment : a comment
Comment : [if IE 9]>IE-specific content<![endif]
Parsing named and numeric character references and converting them to the correct char (note: these 3 references are all equivalent to
'>'
):
>>> parser.feed('>>>')
Named ent: >
Num ent : >
Num ent : >
Feeding incomplete chunks to
feed()
works, but
handle_data()
might be called more than once (unless
convert_charrefs
被设为
True
):
>>> for chunk in ['<sp', 'an>buff', 'ered ', 'text</s', 'pan>']:
... parser.feed(chunk)
...
Start tag: span
Data : buff
Data : ered
Data : text
End tag : span
Parsing invalid HTML (e.g. unquoted attributes) also works:
>>> parser.feed('<p><a class=link href=#main>tag soup</p ></a>')
Start tag: p
Start tag: a
attr: ('class', 'link')
attr: ('href', '#main')
Data : tag soup
End tag : p
End tag : a