Living Code

My copy of the new Python Cookbook arrived today (pretty quick considering my first issue of Make magazine hasn’t arrived yet). It’s pretty cool to see my name in an O’Reilly book, even for only a single recipe. The book looks great too, I think Alex and Anna and David have done a great job and I’m really looking forward to going through it.

Thanks to everyone who replied about the missing word. I’ve been a bit overwhelmed lately and haven’t had a chance to follow up with that, but the responses were all great.

After much delay, my slides are finally up from the VanPyZ talk last week.

Using Python and Cocoa on OS X

Again I’m using Eric Meyer’s S5 tool for HTML slides, but it still ends up being a large download because it includes a completely unneccesary quicktime movie. My daughter and I have been playing with iStopMotion and this was one of our first forays into claymation.

The reason it’s in the slideshow, is that movie making is now completely accessible to an eight-year-old, and I want to writing games and other programs equally accessible to her.

Still a ways to go…

My talk at VanX last night was a success. Not many people showed (too close to Xmas), but the ones who did seemed to enjoy my presentation on Cocoa, Python, and Renaissance. Gerald was a great host, SchemaSoft provided a good (and convenient!) venue, Paul came to show support, and BlastRadius (my employer) sponsored the snacks. After we went to Mira in Yaletown for beers and tech talk, had the whole place to ourselves, and a musician playing Flamenco guitar, then I walked across the bridge to home. A great end to a great evening.

I’ve posted my slides at livingcode.org/slides/renaissance.html using Eric Meyer’s neat S5 tool to put the whole slideshow into one HTML file.

I’ve also built a new .dmg containing all the source code and built, runnable examples (seven of them now), although they’re not all fully functional yet. More example gsmarkup to view, improved setup scripts, and they all have icons now. The file is examples 2004-12-17 on SourceForge.

I’ve been working hard to put this all together, which hasn’t left much time for posting, but I will have a lot more to say real soon now.

OK, time to crank up to speed, it’s been a lot longer than I intended between posts.

In the last episode we learned how to initialize many of the DOMs and DOM-like tools for Python from an XML document. Today we’re going to see how to convert these back to XML from the DOM. So fasten your seatbelts and let’s go.

import domParse

from xml.dom.ext.c14n import Canonicalize

def stringMinidom(filename):

    return Canonicalize(domParse.parseMinidom(filename))

def string4Dom(filename):

    return Canonicalize(domParse.parse4Dom(filename))

def stringDomlette(filename):

    return Canonicalize(domParse.parseDomlette(filename))

def stringLibXml(filename):

    # pretty-printed, which may not be what you want,

    # depending on the XML in question

    return domParse.parseLibXml(filename).serialize(encoding='utf-8', format=True)

    # 4DOM c14n breaks because libXML doesn't give you a DOM

    # return Canonicalize(domParse.parseLibXml(filename))

def stringPxDom(filename):

    import pxdom

    serializer = pxdom.LSSerializer()

    return serializer.writeToString(domParse.parsePxDom(filename))

    #return Canonicalize(domParse.parsePxDom(filename))

def main(filename):

    print '4DOM:', string4Dom(filename)

    print 'Domlette:', stringDomlette(filename)

    print 'MiniDom:', stringMinidom(filename)

    print 'LibXml:', stringLibXml(filename)

    print 'PxDom:', stringPxDom(filename)

if __name__ == '__main__': main(domParse.small_filename)

As you can see, there’s not much to it. This codes does require that you’ve installed the PyXML package, but if you’re serious about XML in Python, that will already be the case. In our next outing we can explore some of the less DOM-like, but more Pythonic ways to play with XML.

PyXML: http://pyxml.sourceforge.net/

4Suite: http://4suite.org/index.xhtml

libxml: http://www.xmlsoft.org/ (instructions for the python bindings are linked from this page)

pxdom: http://www.doxdesk.com/software/py/pxdom.html

You may now return your trays to their upright positions.

There are many DOM options in Python, and I have trouble remembering how to load a document into the various DOMs. Here are a few common ones, although there are many variations on them (loading from URL or string, different configurations, etc.). This should provide a starting point.

# Examples for reading in various DOMs from an XML file

# MiniDOM

def parseMinidom(filename):

    try:

        from xml.dom.minidom import parse

        doc = parse(filename)

        return doc

    except Exception, e:

        return 'parseMinidom() failed with exception %s' % e

# 4DOM

def parse4Dom(filename):

    try:

        from xml.dom.ext.reader.Sax2 import Reader

        f = file(filename)

        reader = Reader(validate=0, keepAllWs=0, catName=None)

        doc = reader.fromStream(f) # slow!

        f.close()

        return doc

    except Exception, e:

        return 'parse4Dom() failed with exception %s' % e

# Domlette

def parseDomlette(filename):

    try:

        from Ft.Xml.Domlette import NonvalidatingReader as reader

        f = file(filename)

        uri = 'file:///%s' % filename # suppress warning

        doc = reader.parseStream(f, uri)

        f.close()

        return doc

    except Exception, e:

        return 'parseDomlette() failed with exception %s' % e

# libXml

def parseLibXml(filename):

    try:

        import libxml2

        f = file(filename)

        data = f.read()

        f.close()

        doc = libxml2.parseDoc(data)

        return doc

    except Exception, e:

        return 'parseLibXml() failed with exception %s' % e

# pxDom

def parsePxDom(filename):

    try:

        import pxdom

        doc = pxdom.parse(filename)

        return doc

    except Exception, e:

        return 'parsePxDom() failed with exception %s' % e

def main():

    import sys

    filename = sys.argv[1]

    print '4DOM:', parse4Dom(filename)

    print 'Domlette:', parseDomlette(filename)

    print 'MiniDom:', parseMinidom(filename)

    print 'LibXml:', parseLibXml(filename)

    print 'PxDom:', parsePxDom(filename)

if __name__ == '__main__': main()