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
|
\section{\module{HTMLParser} ---
Simple HTML and XHTML parser}
\declaremodule{standard}{HTMLParser}
\modulesynopsis{A simple parser that can handle HTML and XHTML.}
\versionadded{2.2}
This module defines a class \class{HTMLParser} which serves as the
basis for parsing text files formatted in HTML\index{HTML} (HyperText
Mark-up Language) and XHTML.\index{XHTML} Unlike the parser in
\refmodule{htmllib}, this parser is not based on the SGML parser in
\refmodule{sgmllib}.
\begin{classdesc}{HTMLParser}{}
The \class{HTMLParser} class is instantiated without arguments.
An 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 \refmodule{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.
\end{classdesc}
An exception is defined as well:
\begin{excdesc}{HTMLParseError}
Exception raised by the \class{HTMLParser} class when it encounters an
error while parsing. This exception provides three attributes:
\member{msg} is a brief message explaining the error, \member{lineno}
is the number of the line on which the broken construct was detected,
and \member{offset} is the number of characters into the line at which
the construct starts.
\end{excdesc}
\class{HTMLParser} instances have the following methods:
\begin{methoddesc}{reset}{}
Reset the instance. Loses all unprocessed data. This is called
implicitly at instantiation time.
\end{methoddesc}
\begin{methoddesc}{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 \method{close()} is called.
\end{methoddesc}
\begin{methoddesc}{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 \method{close()}.
\end{methoddesc}
\begin{methoddesc}{getpos}{}
Return current line number and offset.
\end{methoddesc}
\begin{methoddesc}{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.).
\end{methoddesc}
\begin{methoddesc}{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 \var{tag} argument is the name of the tag converted to
lower case. The \var{attrs} argument is a list of \code{(\var{name},
\var{value})} pairs containing the attributes found inside the tag's
\code{<>} brackets. The \var{name} will be translated to lower case
and double quotes and backslashes in the \var{value} have been
interpreted. For instance, for the tag \code{<A
HREF="http://www.cwi.nl/">}, this method would be called as
\samp{handle_starttag('a', [('href', 'http://www.cwi.nl/')])}.
\end{methoddesc}
\begin{methoddesc}{handle_startendtag}{tag, attrs}
Similar to \method{handle_starttag()}, but called when the parser
encounters an XHTML-style empty tag (\code{<a .../>}). This method
may be overridden by subclasses which require this particular lexical
information; the default implementation simple calls
\method{handle_starttag()} and \method{handle_endtag()}.
\end{methoddesc}
\begin{methoddesc}{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 \var{tag} argument is the name of
the tag converted to lower case.
\end{methoddesc}
\begin{methoddesc}{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.
\end{methoddesc}
\begin{methoddesc}{handle_charref}{name} This method is called to
process a character reference of the form \samp{\&\#\var{ref};}. It
is intended to be overridden by a derived class; the base class
implementation does nothing.
\end{methoddesc}
\begin{methoddesc}{handle_entityref}{name}
This method is called to process a general entity reference of the
form \samp{\&\var{name};} where \var{name} is an general entity
reference. It is intended to be overridden by a derived class; the
base class implementation does nothing.
\end{methoddesc}
\begin{methoddesc}{handle_comment}{data}
This method is called when a comment is encountered. The
\var{comment} argument is a string containing the text between the
\samp{--} and \samp{--} delimiters, but not the delimiters
themselves. For example, the comment \samp{<!--text-->} will
cause this method to be called with the argument \code{'text'}. It is
intended to be overridden by a derived class; the base class
implementation does nothing.
\end{methoddesc}
\begin{methoddesc}{handle_decl}{decl}
Method called when an SGML declaration is read by the parser. The
\var{decl} parameter will be the entire contents of the declaration
inside the \code{<!}...\code{>} markup.It is intended to be overridden
by a derived class; the base class implementation does nothing.
\end{methoddesc}
\begin{methoddesc}{handle_pi}{data}
Method called when a processing instruction is encountered. The
\var{data} parameter will contain the entire processing instruction.
For example, for the processing instruction \code{<?proc color='red'>},
this method would be called as \code{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 \character{?} will cause the \character{?} to be included in
\var{data}.}
\end{methoddesc}
\subsection{Example HTML Parser Application \label{htmlparser-example}}
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:
\begin{verbatim}
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
\end{verbatim}
|
