[XML-SIG] XPath in Python 2

[Mike Olson]

Paul Prescod wrote:
> 
> 
> 4XPath is cleaner from a user's point of view, but it requires a lot bit
> of C/lex code for parsing the XPaths. I don't know if we would have to
> go back to the BDFL to get permission for that code to go into Python.

Or we could re write the parser in C/python.  There has been some talk
of doing it with SRE....

> 
> We also have the option of creating a new XPath implementation also. The
> primary virtue of doing so would be the opportunity to implement a tiny
> subset of XPath in a much smaller amount of code. The two existing
> implementations probably have more code than the rest of the Python 1.6
> XML package. And in 4XPath's case, a lot of that is C code.

Actually, very little is in C.  The generated C is quite large (you've
all seen bison output before), but the "other" c is a very small amount.

Almost all of the functionality is written in python....

Mike


> 
> ---
> 
> My feeling is that implementing 10% of XPath in 10% of the code would
> get us 80% of the benefit. Those that need the rest can download 4XPath.
> I also think that 4XPath should be part of the pyxml distribution.
> 
> The 10% that is most interesting:
> 
>         * a/b/c
>         * a//b
>         * ../
> 
> Actually, that's probably not even 10% and it can be "parsed" mostly
> with a "string.split" on "/". Things like positional predicates can be
> implemented with Python sequence syntax. Attribute access can use DOM
> syntax. All in all, this looks like an afternoon's work, if we agree
> that it should go into Python.
> 
> --
>  Paul Prescod - Not encumbered by corporate consensus
> "Computer Associates is expected to come in with better than expected
> earnings." Bob O'Brien, quoted in
>         - http://www.fool.com/news/2000/foth000316.htm
> 
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-- 
Mike Olson				 Principal Consultant
mike.olson@fourthought.com               (303)583-9900 x 102
Fourthought, Inc.                         http://Fourthought.com 
Software-engineering, knowledge-management, XML, CORBA, Linux, Python