[Python-Dev] Simple xml.sax example?

14 Oct 2000 12:19:20 +0200

* Skip Montanaro
|
| Is there a simple example available that demonstrates how to use
| elements of the new xml.sax package?

Here are a couple from an internal seminar I recently gave on this.  I
could make the slides available as well, if there is interest.

--Lars M.

--- elem_count.py

import sys

from xml.sax import make_parser, handler

class FancyCounter(handler.ContentHandler):

    def __init__(self):
        self._elems = 0
        self._attrs = 0
        self._elem_types = {}
        self._attr_types = {}

    def startElement(self, name, attrs):
        self._elems = self._elems + 1
        self._attrs = self._attrs + len(attrs)
        self._elem_types[name] = self._elem_types.get(name, 0) + 1

        for name in attrs.keys():
            self._attr_types[name] = self._attr_types.get(name, 0) + 1

    def endDocument(self):
        print "There were", self._elems, "elements."
        print "There were", self._attrs, "attributes."

        print "---ELEMENT TYPES"
        for pair in  self._elem_types.items():
            print "%20s %d" % pair

        print "---ATTRIBUTE TYPES"
        for pair in  self._attr_types.items():
            print "%20s %d" % pair

parser = make_parser()
parser.setContentHandler(FancyCounter())
parser.parse(sys.argv[1])

--- roundtrip.py

"""
A simple demo that reads in an XML document and spits out an equivalent,
but not necessarily identical, document.
"""

import sys, string

from xml.sax import saxutils, handler, make_parser

# --- The ContentHandler

class ContentGenerator(handler.ContentHandler):

    def __init__(self, out = sys.stdout):
        handler.ContentHandler.__init__(self)
        self._out = out

    # ContentHandler methods

    def startDocument(self):
        self._out.write('<?xml version="1.0" encoding="iso-8859-1"?>\n')

    def startElement(self, name, attrs):
        self._out.write('<' + name)
        for (name, value) in attrs.items():
            self._out.write(' %s="%s"' % (name, saxutils.escape(value)))
        self._out.write('>')

    def endElement(self, name):
        self._out.write('</%s>' % name)

    def characters(self, content):
        self._out.write(saxutils.escape(content))

    def ignorableWhitespace(self, content):
        self._out.write(content)

    def processingInstruction(self, target, data):
        self._out.write('<?%s %s?>' % (target, data))

# --- The main program

parser = make_parser()
parser.setContentHandler(ContentGenerator())
parser.parse(sys.argv[1])

--- rss2html.py

import sys

from xml.sax import make_parser, handler

# --- Templates

top = \
"""
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
  <TITLE>%s</TITLE>
</HEAD>

<BODY>
<H1>%s</H1>
"""

bottom = \
"""
</ul>

<HR>
<ADDRESS>
Converted to HTML by sax_rss2html.py.
</ADDRESS>

</BODY>
</HTML>
"""

# --- The ContentHandler

class RSSHandler(handler.ContentHandler):

    def __init__(self, out = sys.stdout):
        handler.ContentHandler.__init__(self)
        self._out = out

        self._text = ""
        self._parent = None
        self._list_started = 0
        self._title = None
        self._link = None
        self._descr = ""

    # ContentHandler methods

    def startElement(self, name, attrs):
        if name == "channel" or name == "image" or name == "item":
            self._parent = name

        self._text = ""

    def endElement(self, name):
        if self._parent == "channel":
            if name == "title":
                self._out.write(top % (self._text, self._text))
            elif name == "description":
                self._out.write("<p>%s</p>\n" % self._text)

        elif self._parent == "item":
            if name == "title":
                self._title = self._text
            elif name == "link":
                self._link = self._text
            elif name == "description":
                self._descr = self._text
            elif name == "item":
                if not self._list_started:
                    self._out.write("<ul>\n")
                    self._list_started = 1

                self._out.write('  <li><a href="%s">%s</a> %s\n' %
                                (self._link, self._title, self._descr))

                self._title = None
                self._link = None
                self._descr = ""

        if name == "rss":
            self._out.write(bottom)

    def characters(self, content):
        self._text = self._text + content

# --- Main program

parser = make_parser()
parser.setContentHandler(RSSHandler())
parser.parse(sys.argv[1])