5.7 The formatter Module

The formatter module provides formatter classes that can be used together with the htmllib module.

This module provides two class families, formatters and writers. Formatters convert a stream of tags and data strings from the HTML parser into an event stream suitable for an output device, and writers render that event stream on an output device. Example 5-13 demonstrates.

In most cases, you can use the AbstractFormatter class to do the formatting. It calls methods on the writer object, representing different kinds of formatting events. The AbstractWriter class simply prints a message for each method call.

Example 5-13. Using the formatter Module to Convert HTML to an Event Stream

File: formatter-example-1.py

import formatter
import htmllib

w = formatter.AbstractWriter()
f = formatter.AbstractFormatter(w)

file = open("samples/sample.htm")

p = htmllib.HTMLParser(f)
p.feed(file.read())
p.close()

file.close()

send_paragraph(1)
new_font(('h1', 0, 1, 0))
send_flowing_data('A Chapter.')
send_line_break()
send_paragraph(1)
new_font(None)
send_flowing_data('Some text. Some more text. Some')
send_flowing_data(' ')
new_font((None, 1, None, None))
send_flowing_data('emphasized')
new_font(None)
send_flowing_data(' text. A')
send_flowing_data(' link')
send_flowing_data('[1]')
send_flowing_data('.'

In addition to the AbstractWriter class, the formatter module provides a NullWriter class, which ignores all events passed to it, and a DumbWriter class that converts the event stream to a plain text document, as shown in Example 5-14.

Example 5-14. Using the formatter Module to Convert HTML to Plain Text

File: formatter-example-2.py

import formatter
import htmllib

w = formatter.DumbWriter() # plain text
f = formatter.AbstractFormatter(w)

file = open("samples/sample.htm")

# print html body as plain text
p = htmllib.HTMLParser(f)
p.feed(file.read())
p.close()

file.close()

# print links
print
print
i = 1
for link in p.anchorlist:
    print i, "=>", link
    i = i + 1

A Chapter.

Some text. Some more text. Some emphasized text. A link[1].

1 => http://www.python.org

Example 5-15 provides a custom Writer, which in this case is subclassed from the DumbWriter class. This version keeps track of the current font style and tweaks the output somewhat depending on the font.

Example 5-15. Using the formatter Module with a Custom Writer

File: formatter-example-3.py

import formatter
import htmllib, string

class Writer(formatter.DumbWriter):

    def _ _init_ _(self):
        formatter.DumbWriter._ _init_ _(self)
        self.tag = ""
        self.bold = self.italic = 0
        self.fonts = []

    def new_font(self, font):
        if font is None:
            font = self.fonts.pop()
            self.tag, self.bold, self.italic = font
        else:
            self.fonts.append((self.tag, self.bold, self.italic))
            tag, bold, italic, typewriter = font
            if tag is not None:
                self.tag = tag
            if bold is not None:
                self.bold = bold
            if italic is not None:
                self.italic = italic

    def send_flowing_data(self, data):
        if not data:
            return
        atbreak = self.atbreak or data[0] in string.whitespace
        for word in string.split(data):
            if atbreak:
                self.file.write(" ")
            if self.tag in ("h1", "h2", "h3"):
                word = string.upper(word)
            if self.bold:
                word = "*" + word + "*"
            if self.italic:
                word = "_" + word + "_"
            self.file.write(word)
            atbreak = 1
        self.atbreak = data[-1] in string.whitespace

w = Writer()
f = formatter.AbstractFormatter(w)

file = open("samples/sample.htm")

# print html body as plain text
p = htmllib.HTMLParser(f)
p.feed(file.read())
p.close()

_A_ _CHAPTER._

Some text. Some more text. Some *emphasized* text. A link[1].