mirror of
https://github.com/python/cpython.git
synced 2025-11-03 19:34:08 +00:00
274 lines
9.6 KiB
TeX
274 lines
9.6 KiB
TeX
\section{Standard Module \sectcode{htmllib}}
|
|
\stmodindex{htmllib}
|
|
\index{HTML}
|
|
\index{hypertext}
|
|
|
|
\renewcommand{\indexsubitem}{(in module htmllib)}
|
|
|
|
This module defines a number of classes which can serve as a basis for
|
|
parsing text files formatted in HTML (HyperText Mark-up Language).
|
|
The classes are not directly concerned with I/O --- the have to be fed
|
|
their input in string form, and will make calls to methods of a
|
|
``formatter'' object in order to produce output. The classes are
|
|
designed to be used as base classes for other classes in order to add
|
|
functionality, and allow most of their methods to be extended or
|
|
overridden. In turn, the classes are derived from and extend the
|
|
class \code{SGMLParser} defined in module \code{sgmllib}.
|
|
\index{SGML}
|
|
\stmodindex{sgmllib}
|
|
\ttindex{SGMLParser}
|
|
\index{formatter}
|
|
|
|
The following is a summary of the interface defined by
|
|
\code{sgmllib.SGMLParser}:
|
|
|
|
\begin{itemize}
|
|
|
|
\item
|
|
The interface to feed data to an instance is through the \code{feed()}
|
|
method, which takes a string argument. This can be called with as
|
|
little or as much text at a time as desired;
|
|
\code{p.feed(a); p.feed(b)} has the same effect as \code{p.feed(a+b)}.
|
|
When the data contains complete
|
|
HTML elements, these are processed immediately; incomplete elements
|
|
are saved in a buffer. To force processing of all unprocessed data,
|
|
call the \code{close()} method.
|
|
|
|
Example: to parse the entire contents of a file, do\\
|
|
\code{parser.feed(open(file).read()); parser.close()}.
|
|
|
|
\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 the following classes:
|
|
|
|
\begin{funcdesc}{HTMLParser}{}
|
|
This is the most basic HTML parser class. It defines one additional
|
|
entity name over the names defined by the \code{SGMLParser} base
|
|
class, \code{\•}. It also defines handlers for the following
|
|
tags: \code{<LISTING>...</LISTING>}, \code{<XMP>...</XMP>}, and
|
|
\code{<PLAINTEXT>} (the latter is terminated only by end of file).
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{CollectingParser}{}
|
|
This class, derived from \code{HTMLParser}, collects various useful
|
|
bits of information from the HTML text. To this end it defines
|
|
additional handlers for the following tags: \code{<A>...</A>},
|
|
\code{<HEAD>...</HEAD>}, \code{<BODY>...</BODY>},
|
|
\code{<TITLE>...</TITLE>}, \code{<NEXTID>}, and \code{<ISINDEX>}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{FormattingParser}{formatter\, stylesheet}
|
|
This class, derived from \code{CollectingParser}, interprets a wide
|
|
selection of HTML tags so it can produce formatted output from the
|
|
parsed data. It is initialized with two objects, a \var{formatter}
|
|
which should define a number of methods to format text into
|
|
paragraphs, and a \var{stylesheet} which defines a number of static
|
|
parameters for the formatting process. Formatters and style sheets
|
|
are documented later in this section.
|
|
\index{formatter}
|
|
\index{style sheet}
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{AnchoringParser}{formatter\, stylesheet}
|
|
This class, derived from \code{FormattingParser}, extends the handling
|
|
of the \code{<A>...</A>} tag pair to call the formatter's
|
|
\code{bgn_anchor()} and \code{end_anchor()} methods. This allows the
|
|
formatter to display the anchor in a different font or color, etc.
|
|
\end{funcdesc}
|
|
|
|
Instances of \code{CollectingParser} (and thus also instances of
|
|
\code{FormattingParser} and \code{AnchoringParser}) have the following
|
|
instance variables:
|
|
|
|
\begin{datadesc}{anchornames}
|
|
A list of the values of the \code{NAME} attributes of the \code{<A>}
|
|
tags encountered.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{anchors}
|
|
A list of the values of \code{HREF} attributes of the \code{<A>} tags
|
|
encountered.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{anchortypes}
|
|
A list of the values of the \code{TYPE} attributes of the \code{<A>}
|
|
tags encountered.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{inanchor}
|
|
Outside an \code{<A>...</A>} tag pair, this is zero. Inside such a
|
|
pair, it is a unique integer, which is positive if the anchor has a
|
|
\code{HREF} attribute, negative if it hasn't. Its absolute value is
|
|
one more than the index of the anchor in the \code{anchors},
|
|
\code{anchornames} and \code{anchortypes} lists.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{isindex}
|
|
True if the \code{<ISINDEX>} tag has been encountered.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{nextid}
|
|
The attribute list of the last \code{<NEXTID>} tag encountered, or
|
|
an empty list if none.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{title}
|
|
The text inside the last \code{<TITLE>...</TITLE>} tag pair, or
|
|
\code{''} if no title has been encountered yet.
|
|
\end{datadesc}
|
|
|
|
The \code{anchors}, \code{anchornames} and \code{anchortypes} lists
|
|
are ``parallel arrays'': items in these lists with the same index
|
|
pertain to the same anchor. Missing attributes default to the empty
|
|
string. Anchors with neither a \code{HREF} nor a \code{NAME}
|
|
attribute are not entered in these lists at all.
|
|
|
|
The module also defines a number of style sheet classes. These should
|
|
never be instantiated --- their class variables are the only behavior
|
|
required. Note that style sheets are specifically designed for a
|
|
particular formatter implementation. The currently defined style
|
|
sheets are:
|
|
\index{style sheet}
|
|
|
|
\begin{datadesc}{NullStylesheet}
|
|
A style sheet for use on a dumb output device such as an \ASCII{}
|
|
terminal.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{X11Stylesheet}
|
|
A style sheet for use with an X11 server.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{MacStylesheet}
|
|
A style sheet for use on Apple Macintosh computers.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{StdwinStylesheet}
|
|
A style sheet for use with the \code{stdwin} module; it is an alias
|
|
for either \code{X11Stylesheet} or \code{MacStylesheet}.
|
|
\bimodindex{stdwin}
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{GLStylesheet}
|
|
A style sheet for use with the SGI Graphics Library and its font
|
|
manager (the SGI-specific built-in modules \code{gl} and \code{fm}).
|
|
\bimodindex{gl}
|
|
\bimodindex{fm}
|
|
\end{datadesc}
|
|
|
|
Style sheets have the following class variables:
|
|
|
|
\begin{datadesc}{stdfontset}
|
|
A list of up to four font definititions, respectively for the roman,
|
|
italic, bold and constant-width variant of a font for normal text. If
|
|
the list contains less than four font definitions, the last item is
|
|
used as the default for missing items. The type of a font definition
|
|
depends on the formatter in use; its only use is as a parameter to the
|
|
formatter's \code{setfont()} method.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{h1fontset}
|
|
\dataline{h2fontset}
|
|
\dataline{h3fontset}
|
|
The font set used for various headers (text inside \code{<H1>...</H1>}
|
|
tag pairs etc.).
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{stdindent}
|
|
The indentation of normal text. This is measured in the ``native''
|
|
units of the formatter in use; for some formatters these are
|
|
characters, for others (especially those that actually support
|
|
variable-spacing fonts) in pixels or printer points.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{ddindent}
|
|
The indentation used for the first level of \code{<DD>} tags.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{ulindent}
|
|
The indentation used for the first level of \code{<UL>} tags.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{h1indent}
|
|
The indentation used for level 1 headers.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{h2indent}
|
|
The indentation used for level 2 headers.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{literalindent}
|
|
The indentation used for literal text (text inside
|
|
\code{<PRE>...</PRE>} and similar tag pairs).
|
|
\end{datadesc}
|
|
|
|
Although no documented implementation of a formatter exists, the
|
|
\code{FormattingParser} class assumes that formatters have a
|
|
certain interface. This interface requires the following methods:
|
|
\index{formatter}
|
|
|
|
\begin{funcdesc}{setfont}{fontspec}
|
|
Set the font to be used subsequently. The \var{fontspec} argument is
|
|
an item in a style sheet's font set.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{flush}{}
|
|
Finish the current line, if not empty, and begin a new one.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{setleftindent}{n}
|
|
Set the left indentation of the following lines to \var{n} units.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{needvspace}{n}
|
|
Require at least \var{n} blank lines before the next line. Implies
|
|
\code{flush()}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{addword}{word\, space}
|
|
Add a \var{word} to the current paragraph, followed by \var{space}
|
|
spaces.
|
|
\end{funcdesc}
|
|
|
|
\begin{datadesc}{nospace}
|
|
If this instance variable is true, empty words should be ignored by
|
|
\code{addword}. It should be set to false after a non-empty word has
|
|
been added.
|
|
\end{datadesc}
|
|
|
|
\begin{funcdesc}{setjust}{justification}
|
|
Set the justification of the current paragraph. The
|
|
\var{justification} can be \code{'c'} (center), \code{'l'} (left
|
|
justified), \code{'r'} (right justified) or \code{'lr'} (left and
|
|
right justified).
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{bgn_anchor}{id}
|
|
Begin an anchor. The \var{id} parameter is the value of the parser's
|
|
\code{inanchor} attribute.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{end_anchor}{id}
|
|
End an anchor. The \var{id} parameter is the value of the parser's
|
|
\code{inanchor} attribute.
|
|
\end{funcdesc}
|
|
|
|
A sample formatter implementation can be found in the module
|
|
\code{fmt}, which in turn uses the module \code{Para}. These modules are
|
|
not intended as standard library modules; they are available as an
|
|
example of how to write a formatter.
|
|
\ttindex{fmt}
|
|
\ttindex{Para}
|