1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
|
:mod:`html.parser` --- Simple HTML and XHTML parser
===================================================
.. module:: html.parser
:synopsis: A simple parser that can handle HTML and XHTML.
**Source code:** :source:`Lib/html/parser.py`
.. 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.
.. class:: HTMLParser(*, 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 :class:`.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 :class:`.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.
.. versionchanged:: 3.4
*convert_charrefs* keyword argument added.
.. versionchanged:: 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
:class:`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:
.. code-block:: none
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
:class:`.HTMLParser` Methods
----------------------------
:class:`HTMLParser` instances have the following methods:
.. 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. *data* must be :class:`str`.
.. 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.reset()
Reset the instance. Loses all unprocessed data. This is called implicitly at
instantiation time.
.. 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.).
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 :meth:`~HTMLParser.handle_startendtag`):
.. method:: HTMLParser.handle_starttag(tag, attrs)
This method is called to handle the start tag of an element (e.g. ``<div id="main">``).
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="https://www.cwi.nl/">``, this method
would be called as ``handle_starttag('a', [('href', 'https://www.cwi.nl/')])``.
All entity references from :mod:`html.entities` are replaced in the attribute
values.
.. method:: HTMLParser.handle_endtag(tag)
This method is called to handle the end tag of an element (e.g. ``</div>``).
The *tag* argument is the name of the tag converted to lower case.
.. method:: HTMLParser.handle_startendtag(tag, attrs)
Similar to :meth:`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 :meth:`handle_starttag` and :meth:`handle_endtag`.
.. method:: 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>``).
.. method:: 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``.
.. method:: HTMLParser.handle_charref(name)
This method is called to process decimal and hexadecimal numeric character
references of the form :samp:`&#{NNN};` and :samp:`&#x{NNN};`. 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``.
.. method:: 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]'``.
.. method:: HTMLParser.handle_decl(decl)
This method is called to handle an HTML doctype declaration (e.g.
``<!DOCTYPE html>``).
The *decl* parameter will be the entire contents of the declaration inside
the ``<!...>`` markup (e.g. ``'DOCTYPE html'``).
.. 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*.
.. method:: HTMLParser.unknown_decl(data)
This method is called when an unrecognized 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 does nothing.
.. _htmlparser-examples:
Examples
--------
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()
Parsing a 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
Parsing comments::
>>> 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 :meth:`~HTMLParser.feed` works, but
:meth:`~HTMLParser.handle_data` might be called more than once
(unless *convert_charrefs* is set to ``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
|
