sgmllib
— 简单 SGML 剖析器
¶
Deprecated since version 2.6:
The
sgmllib
module has been removed in Python 3.
此模块定义的类
SGMLParser
which serves as the basis for parsing text files formatted in SGML (Standard Generalized Mark-up Language). In fact, it does not provide a full SGML parser — it only parses SGML insofar as it is used by HTML, and the module only exists as a base for the
htmllib
module. Another HTML parser which supports XHTML and offers a somewhat different interface is available in the
HTMLParser
模块。
sgmllib.
SGMLParser
¶
The
SGMLParser
class is instantiated without arguments. The parser is hardcoded to recognize the following constructs:
Opening and closing tags of the form
<tag attr="value" ...>
and
</tag>
，分别。
Numeric character references of the form
&#name;
.
Entity references of the form
&name;
.
SGML comments of the form
<!--text-->
. Note that spaces, tabs, and newlines are allowed between the trailing
>
and the immediately preceding
--
.
A single exception is defined as well:
sgmllib.
SGMLParseError
¶
异常被引发通过
SGMLParser
class when it encounters an error while parsing.
2.1 版新增。
SGMLParser
实例具有下列方法：
SGMLParser.
reset
(
)
¶
Reset the instance. Loses all unprocessed data. This is called implicitly at instantiation time.
Stop processing tags. Treat all following input as literal input (CDATA). (This is only provided so the HTML tag
<PLAINTEXT>
can be implemented.)
SGMLParser.
setliteral
(
)
¶
Enter literal mode (CDATA mode).
SGMLParser.
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。
SGMLParser.
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
close()
.
SGMLParser.
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.).
SGMLParser.
handle_starttag
(
tag
,
方法
,
属性
)
¶
This method is called to handle start tags for which either a
start_tag()
or
do_tag()
method has been defined. The
tag
argument is the name of the tag converted to lower case, and the
方法
argument is the bound method which should be used to support semantic interpretation of the start tag. The
属性
argument is a list of
(name, value)
pairs containing the attributes found inside the tag’s
<>
brackets.
The
name
has been translated to lower case. Double quotes and backslashes in the
value
have been interpreted, as well as known character references and known entity references terminated by a semicolon (normally, entity references can be terminated by any non-alphanumerical character, but this would break the very common case of
<A HREF="url?spam=1&eggs=2">
当
eggs
is a valid entity name).
For instance, for the tag
<A HREF="http://www.cwi.nl/">
, this method would be called as
unknown_starttag('a', [('href', 'http://www.cwi.nl/')])
. The base implementation simply calls
方法
with
属性
as the only argument.
New in version 2.5: Handling of entity and character references within attribute values.
SGMLParser.
handle_endtag
(
tag
,
方法
)
¶
This method is called to handle endtags for which an
end_tag()
method has been defined. The
tag
argument is the name of the tag converted to lower case, and the
方法
argument is the bound method which should be used to support semantic interpretation of the end tag. If no
end_tag()
method is defined for the closing element, this handler is not called. The base implementation simply calls
方法
.
SGMLParser.
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.
SGMLParser.
handle_charref
(
ref
)
¶
This method is called to process a character reference of the form
&#ref;
. The base implementation uses
convert_charref()
to convert the reference to a string. If that method returns a string, it is passed to
handle_data()
，否则
unknown_charref(ref)
is called to handle the error.
Changed in version 2.5:
使用
convert_charref()
instead of hard-coding the conversion.
SGMLParser.
convert_charref
(
ref
)
¶
Convert a character reference to a string, or
None
.
ref
is the reference passed in as a string. In the base implementation,
ref
must be a decimal number in the range 0–255. It converts the code point found using the
convert_codepoint()
方法。若
ref
is invalid or out of range, this method returns
None
. This method is called by the default
handle_charref()
implementation and by the attribute value parser.
2.5 版新增。
SGMLParser.
convert_codepoint
(
codepoint
)
¶
Convert a code point to a
str
value. Encodings can be handled here if appropriate, though the rest of
sgmllib
is oblivious on this matter.
2.5 版新增。
SGMLParser.
handle_entityref
(
ref
)
¶
This method is called to process a general entity reference of the form
&ref;
where
ref
is a general entity reference. It converts
ref
by passing it to
convert_entityref()
. If a translation is returned, it calls the method
handle_data()
with the translation; otherwise, it calls the method
unknown_entityref(ref)
。默认
entitydefs
defines translations for
&
,
'
,
>
,
<
，和
"
.
Changed in version 2.5:
使用
convert_entityref()
instead of hard-coding the conversion.
SGMLParser.
convert_entityref
(
ref
)
¶
Convert a named entity reference to a
str
value, or
None
. The resulting value will not be parsed.
ref
will be only the name of the entity. The default implementation looks for
ref
in the instance (or class) variable
entitydefs
which should be a mapping from entity names to corresponding translations. If no translation is available for
ref
, this method returns
None
. This method is called by the default
handle_entityref()
implementation and by the attribute value parser.
2.5 版新增。
SGMLParser.
handle_comment
(
comment
)
¶
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'
. The default method does nothing.
SGMLParser.
handle_decl
(
data
)
¶
Method called when an SGML declaration is read by the parser. In practice, the
DOCTYPE
declaration is the only thing observed in HTML, but the parser does not discriminate among different (or broken) declarations. Internal subsets in a
DOCTYPE
declaration are not supported. The
data
parameter will be the entire contents of the declaration inside the
<!
…
>
markup. The default implementation does nothing.
SGMLParser.
report_unbalanced
(
tag
)
¶
This method is called when an end tag is found which does not correspond to any open element.
SGMLParser.
unknown_starttag
(
tag
,
属性
)
¶
This method is called to process an unknown start tag. It is intended to be overridden by a derived class; the base class implementation does nothing.
SGMLParser.
unknown_endtag
(
tag
)
¶
This method is called to process an unknown end tag. It is intended to be overridden by a derived class; the base class implementation does nothing.
SGMLParser.
unknown_charref
(
ref
)
¶
This method is called to process unresolvable numeric character references. Refer to
handle_charref()
to determine what is handled by default. It is intended to be overridden by a derived class; the base class implementation does nothing.
SGMLParser.
unknown_entityref
(
ref
)
¶
This method is called to process an unknown entity reference. It is intended to be overridden by a derived class; the base class implementation does nothing.
Apart from overriding or extending the methods listed above, derived classes may also define methods of the following form to define processing of specific tags. Tag names in the input stream are case independent; the tag occurring in method names must be in lower case:
SGMLParser.
start_tag
(
属性
)
This method is called to process an opening tag
tag
. It has preference over
do_tag()
。
属性
argument has the same meaning as described for
handle_starttag()
above.
SGMLParser.
do_tag
(
属性
)
This method is called to process an opening tag
tag
for which no
start_tag()
method is defined. The
属性
argument has the same meaning as described for
handle_starttag()
above.
SGMLParser.
end_tag
(
)
This method is called to process a closing tag tag .
Note that the parser maintains a stack of open elements for which no end tag has been found yet. Only tags processed by
start_tag()
are pushed on this stack. Definition of an
end_tag()
method is optional for these tags. For tags processed by
do_tag()
或通过
unknown_tag()
, no
end_tag()
method must be defined; if defined, it will not be used. If both
start_tag()
and
do_tag()
methods exist for a tag, the
start_tag()
method takes precedence.