RE: [Jython-users] Accessing Jython Regular Expressions from java

[Guy Gascoigne-P. <gg...@tr...>]

I guess that I didn't explain my self very clearly, though I think that you
did answer my question.  I've written a java module that extends jython, I
want that java module to use regular expressions in the same way that jython
does.  As you say that would involve using sre and I can't do that from a
java module :-(

Thanks - Guy

-----Original Message-----
From: bc...@wo... [mailto:bc...@wo...] 
Sent: Wednesday, February 06, 2002 12:29 AM
To: 'jyt...@li...'
Cc: Guy Gascoigne-Piggford
Subject: Re: [Jython-users] Accessing Jython Regular Expressions from java

[Guy Gascoigne-Piggford]

>OK, so I was happily just using the oromatcher Perl5Compiler() routines to
>handle python style regular expressions in my java code.  Basically the
>regular expressions get passed from the jython script through to a java
>function of mine and I wanted to handle them in a python compatible way.
It
>turns out that I wasn't completely correct.
> 
>I got code that actually worked pretty well until I started passing
>expressions such as this to it:
> 
>"(source filename|Name of).*\?(?i)"
> 
>The gotcha is the (?i) bit at the end, this generates a mismatched
>parenthesis error.

I'm a little confused here. Are you reporting a bug in the way jython
does regular expression or in way Perl5Compiler does them?

>Now after a lot of delving I've discovered that jython actually uses a
>completely different regular expression library - the one in the sre
module.
>My question is, since this is all python code, is there any way that I can
>just call out to this from java?

So you want to use sre from a pure java (no jython) application? If that
is what you're asking, the answer is no, it can't be done.

>It appears to me that by moving over to a
>python implementation here I can't use the same stuff - so far I've found
>one incompatibility between the two implementations, and I'm concerned that
>I'll run into others.

My confusion continues. I can compile the example re you gave with
jython-2.1 without any errors:

Jython 2.1 on java1.4.0-beta3 (JIT: null)
Type "copyright", "credits" or "license" for more information.
>>> import re
>>> re.compile("(source filename|Name of).*\?(?i)")
org.python.modules.sre.PatternObject@dd5a3d
 
>Am I stuck with pre-processing the regular expressions and handling the
(?i)
>construct myself - I can't believe that's all that there is to it.

The old Perl5Compiler based "pre" module did some fixup of the pattern
before passing the pattern to Perl5Compiler. Se RegexObject.fixPattern()
for details.
 
>Any other alternatives?
> 
>As an aside, why the switch to sre?  Faster?

No.

>Better Python compatibility?

Yes. The "pre" module have some known bugs in it. For example the parens
counting in fixPattern doesn't work in all cases.

regards,
finn