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