mirror of https://github.com/python/cpython
124 lines
5.1 KiB
TeX
124 lines
5.1 KiB
TeX
\section{Standard Module \sectcode{htmllib}}
|
|
\label{module-htmllib}
|
|
\stmodindex{htmllib}
|
|
\index{HTML}
|
|
\index{hypertext}
|
|
|
|
\renewcommand{\indexsubitem}{(in module htmllib)}
|
|
|
|
This module defines a class which can serve as a base for parsing text
|
|
files formatted in the HyperText Mark-up Language (HTML). The class
|
|
is not directly concerned with I/O --- it must be provided with input
|
|
in string form via a method, and makes calls to methods of a
|
|
``formatter'' object in order to produce output. The
|
|
\class{HTMLParser} class is designed to be used as a base class for
|
|
other classes in order to add functionality, and allows most of its
|
|
methods to be extended or overridden. In turn, this class is derived
|
|
from and extends the \class{SGMLParser} class defined in module
|
|
\module{sgmllib}\refstmodindex{sgmllib}. The \class{HTMLParser}
|
|
implementation supports the HTML 2.0 language as described in
|
|
\rfc{1866}. Two implementations of formatter objects are provided in
|
|
the \module{formatter}\refstmodindex{formatter} module; refer to the
|
|
documentation for that module for information on the formatter
|
|
interface.
|
|
\index{SGML}
|
|
\ttindex{SGMLParser}
|
|
\index{formatter}
|
|
|
|
The following is a summary of the interface defined by
|
|
\class{sgmllib.SGMLParser}:
|
|
|
|
\begin{itemize}
|
|
|
|
\item
|
|
The interface to feed data to an instance is through the \method{feed()}
|
|
method, which takes a string argument. This can be called with as
|
|
little or as much text at a time as desired; \samp{p.feed(a);
|
|
p.feed(b)} has the same effect as \samp{p.feed(a+b)}. When the data
|
|
contains complete HTML tags, these are processed immediately;
|
|
incomplete elements are saved in a buffer. To force processing of all
|
|
unprocessed data, call the \method{close()} method.
|
|
|
|
For example, to parse the entire contents of a file, use:
|
|
\bcode\begin{verbatim}
|
|
parser.feed(open('myfile.html').read())
|
|
parser.close()
|
|
\end{verbatim}\ecode
|
|
%
|
|
\item
|
|
The interface to define semantics for HTML tags is very simple: derive
|
|
a class and define methods called \code{start_\var{tag}()},
|
|
\code{end_\var{tag}()}, or \code{do_\var{tag}()}. The parser will
|
|
call these at appropriate moments: \code{start_\var{tag}} or
|
|
\code{do_\var{tag}()} is called when an opening tag of the form
|
|
\code{<\var{tag} ...>} is encountered; \code{end_\var{tag}()} is called
|
|
when a closing tag of the form \code{<\var{tag}>} is encountered. If
|
|
an opening tag requires a corresponding closing tag, like \code{<H1>}
|
|
... \code{</H1>}, the class should define the \code{start_\var{tag}()}
|
|
method; if a tag requires no closing tag, like \code{<P>}, the class
|
|
should define the \code{do_\var{tag}()} method.
|
|
|
|
\end{itemize}
|
|
|
|
The module defines a single class:
|
|
|
|
\begin{funcdesc}{HTMLParser}{formatter}
|
|
This is the basic HTML parser class. It supports all entity names
|
|
required by the HTML 2.0 specification (\rfc{1866}). It also defines
|
|
handlers for all HTML 2.0 and many HTML 3.0 and 3.2 elements.
|
|
\end{funcdesc}
|
|
|
|
In addition to tag methods, the \class{HTMLParser} class provides some
|
|
additional methods and instance variables for use within tag methods.
|
|
|
|
\renewcommand{\indexsubitem}{(HTMLParser attribute)}
|
|
|
|
\begin{datadesc}{formatter}
|
|
This is the formatter instance associated with the parser.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{nofill}
|
|
Boolean flag which should be true when whitespace should not be
|
|
collapsed, or false when it should be. In general, this should only
|
|
be true when character data is to be treated as ``preformatted'' text,
|
|
as within a \code{<PRE>} element. The default value is false. This
|
|
affects the operation of \method{handle_data()} and \method{save_end()}.
|
|
\end{datadesc}
|
|
|
|
\renewcommand{\indexsubitem}{(HTMLParser method)}
|
|
|
|
\begin{funcdesc}{anchor_bgn}{href\, name\, type}
|
|
This method is called at the start of an anchor region. The arguments
|
|
correspond to the attributes of the \code{<A>} tag with the same
|
|
names. The default implementation maintains a list of hyperlinks
|
|
(defined by the \code{href} attribute) within the document. The list
|
|
of hyperlinks is available as the data attribute \code{anchorlist}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{anchor_end}{}
|
|
This method is called at the end of an anchor region. The default
|
|
implementation adds a textual footnote marker using an index into the
|
|
list of hyperlinks created by \method{anchor_bgn()}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{handle_image}{source\, alt\optional{\, ismap\optional{\, align\optional{\, width\optional{\, height}}}}}
|
|
This method is called to handle images. The default implementation
|
|
simply passes the \var{alt} value to the \method{handle_data()}
|
|
method.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{save_bgn}{}
|
|
Begins saving character data in a buffer instead of sending it to the
|
|
formatter object. Retrieve the stored data via \method{save_end()}.
|
|
Use of the \method{save_bgn()} / \method{save_end()} pair may not be
|
|
nested.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{save_end}{}
|
|
Ends buffering character data and returns all data saved since the
|
|
preceeding call to \method{save_bgn()}. If the \code{nofill} flag is
|
|
false, whitespace is collapsed to single spaces. A call to this
|
|
method without a preceeding call to \method{save_bgn()} will raise a
|
|
\exception{TypeError} exception.
|
|
\end{funcdesc}
|