It’s been an exhausting past couple of weeks, but life goes on. WebPath made front page at next.yahoo. I’m starting to get feedback from developers who are actually using it, filing bugs, suggesting features, and it’s gratifying. The community is still building up. Won’t you join too? -m

WebPath, my experimental XPath 2.0 engine in Python is now an open source project with a liberal BSD license. I originally developed this during a Yahoo! Hack Day, and now I get to announce it during another Hack Day. Seems appropriate.

The focus of WebPath was rapid development and providing an experimental platform. There remains tons of potential work left to do on it…watch this space for continued discussion. I’d like to call out special thanks to the Yahoo! management for supporting me on this, and to Douglas Crockford for turning me on to Top Down Operator Precedence parsers. Have a look at the code. You might be pleasantly surprised at how small and simple a basic XPath 2 engine can be. So, who’s up for some XPath hacking?

Code download. (Coming to SourceForge with CVS, etc., in however many days it takes them to approve a new project) I hope this inspires more developers to work on similar projects, or better yet, on this one! -m

I’m taking some time off from work to relax a bit. And just in time for that, my OLPC arrived. Check out the photoset on Flickr. It’s an impressive little machine, and I’m very happy to have got this instead of a Kindle. :)

-m

Here’s the slides from my presentation at XML 2007, dealing with an implementation of XPath 2.0 in Python. I hope to have even more news in this area soon.

WebPath (html)

WebPath (OpenDocument, 4.7 megs)

Did you notice the OpenOffice has nice slide export, that generates both graphically-accurate slides and highly indexable and accessible text versons? -m

Watch this space for details. I’ll be speaking about something related to Python and XPath 2.0. Watch this blog for tidbits on the subject. :) -m

Based on Doug Crockford’s chapter in Beautiful Code, I wanted to take a crack at implementing Top Down Operator Precedence in Python. After all, Python and JavaScript are quite similar, right?

Not really. As you can imagine, Doug’s code makes great use of JavaScript’s strengths, in this case the ability to assign new methods to any object. For an initial version, I wanted to make the Python version behave the same way, as opposed to a deeper redesign that would be more pythonic. (That would come later.)
My initial approach was a __getattr__ method that consisted simply of return getattr(self.prototype, name). When reattaching a new method to an instance, I needed an extra wrapper, done through a wrap method which consisted of return new.instancemethod(method, self, self.__class__). It would be used like this: obj.method = obj.wrap(some_func).

This caused a subtle problem that took me a while to track down. In JavaScript, any function can reference the built-in this variable, which works whether the function is bound to some specific object or not. (Even global functions are bound to the global object.) But Python doesn’t have such a keyword. The language prefers the explicit, and uses a explicitly passed parameter, called by convention self. The call to wrap a specific function also had the effect of binding the self parameter to that particular object; even if it later became a prototype for some other object. This manifested itself as all kinds of broken behavior. For example, the original code has a global scope object, and every time a new scope was entered, the global pointed to a newer object that kept a reference to the rest of the scope chain. But in the object’s methods, self pointed to something different than the global. Messy.

Before I get into solutions, I’d like to see what readers say. How would you go about implementing prototypical inheritance in Python? And what is a more pythonic way to accomplish the same thing? Comment below. Thanks! -m

I’ve always had a thing for text analysis.

• the 352
• and 250
• to 225
• of 188
• in 118
• a 108
• we 100
• is 76
• our 75
• that 72

Source. -m

Link. -m

Check out this script. -m