[pylucene-dev] why isn't my custom Similarityobjectchangingthebehavior?

[Pete]

On Thursday March 15 2007 9:28 pm, Ofer Nave wrote:
> > -----Original Message-----
> > From: pylucene-dev-bounces at osafoundation.org
> > [mailto:pylucene-dev-bounces at osafoundation.org] On Behalf Of Pete
> > Sent: Thursday, March 15, 2007 5:54 PM
> > To: pylucene-dev at osafoundation.org
> > Subject: Re: [pylucene-dev] why isn't my custom
> > Similarityobjectchangingthebehavior?
> >
> > On Thursday March 15 2007 6:31 pm, Ofer Nave wrote:

> > Python doesn't do signature-overloading.  Your class is going
> > to end up with the last definition of idf()
>
> I knew Python didn't have signature overloading, but didn't know what would
> happen when I defined the same function three times.  Frankly, I was
> surprised that it compiled without error.  :)  Thanks for the tip re last
> definition being used.

There's no compilation - Python's entirely interpreted.  Unless you have a 
SyntaxError, the interpreter will let you write whatever code you want.  
Including defining names multiple times, redefining 
variables/functions/classes at runtime and referencing names that don't exist 
(which'll throw an exception at runtime, when you actually hit that code).

> > Looks pretty much right to me - you might think about passing
> > in self.super as an arg to __init__ instead.
>
> Do you mean just to avoid the overhead of creating the inner
> PyLucene.DefaultSimilarity() multiple times if SimilaritySansTF is created
> several times?

No, just that's it a little more flexible - you could pass in some other 
Similarity if you wanted to.  Delegator pattern, or Wrapper, or whatever you 
like to call it[0]. Overhead's not really an issue here, as you're gonna 
create one of these things & pass it to your searcher.

I'd prolly do something like:

def __init__(self, similarity=None);
     similarity=similarity or PyLucene.DefaultSimilarity()
     assert isinstance(similarity, PyLucene.Similarity)
     # should probably name this attr 'similarity', self.super looks weird,
     # but that's just style
     self.super=similarity

I may have some of the above names wrong, but you get the idea.

> > FWIW, if you're new to python, you picked about the single
> > strangest package out there to start with. [0]
>
> Don't I know it. :) Well, whatever doesn't kill you makes you stronger (or
> gets you fired for taking too long).

Heh.  Good luck.

--Pete

[0] - FWIW, doing it this way is an oddity of PyLucene.  In regular Python, 
you'd just subclass & override the method in question.

-- 
Peter Fein   ||   773-575-0694   ||   pfein at pobox.com
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