[XML-SIG] Amara xml_xpath() behaviour

[Luis Miguel Morillas]

2007/12/5, Elston, Gareth R <gelston at doosanbabcock.com>:
> Hi,
>
> I'm new to XML and I've just started using Amara - I'm very impressed.
>
> I've been trying to use xml_xpath() on a bindery object itself created
> with xml_xpath(). I didn't get what I expected, which may be my
> misunderstanding of what xml_xpath() is doing. Here's a short example to
> illustrate (I'm using Amara 1.2.0.2 and Python 2.4.3 on Windows XP.):
>
> In [1]: import amara
>
> In [2]: l = amara.parse('file:///F:/lines.xml')
>
> In [3]: print l.xml()
> <?xml version="1.0" encoding="UTF-8"?>
> <Lines>
>   <Line>
>     <Point x2="1.0" x1="1.0"/>
>     <Point x2="2.0" x1="1.0"/>
>   </Line>
>   <Line>
>     <Point x2="2.0" x1="2.0"/>
>     <Point x2="3.0" x1="2.0"/>
>   </Line>
>   <Line>
>     <Point x2="3.0" x1="3.0"/>
>     <Point x2="5.0" x1="3.0"/>
>   </Line>
> </Lines>
>
> In [4]: l.xml_xpath('//Line')
> Out[4]:
> [<amara.bindery.Line object at 0x015628D0>,
>  <amara.bindery.Line object at 0x0169E6B0>,
>  <amara.bindery.Line object at 0x01759D10>]
>
> In [5]: print l.xml_xpath('//Line')[0].xml()
> <Line>
>     <Point x2="1.0" x1="1.0"/>
>     <Point x2="2.0" x1="1.0"/>
>   </Line>
>
> In [6]: l.xml_xpath('//Line')[0].xml_xpath('//Point')
> Out[6]:
> [<amara.bindery.Point object at 0x0169E210>,
>  <amara.bindery.Point object at 0x0169E250>,
>  <amara.bindery.Point object at 0x0169EA50>,
>  <amara.bindery.Point object at 0x01759CD0>,
>  <amara.bindery.Point object at 0x01759D50>,
>  <amara.bindery.Point object at 0x01759D90>]
>
> I expected only 2 amara.bindery.Point objects in the last step. Is this
> (all 6 Points in the XML data) the expected behaviour?
>

About XPath: http://www.w3.org/TR/xpath

//Point selects all the Point descendants of the document root.

l.xml_xpath('//Line')[0].xml_xpath('Point')

or better:
l.xml_xpath('//Line[1]/Point')

But, be care because amara xpath has some problems ordering nodes (see
http://lists.fourthought.com/pipermail/4suite/2007-June/008285.html)
and it will not be fixed until amara 2.0

-- lm