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XML, Python, xpath: returning empty list


I am trying to read the Length of all the Field nodes of my xml file using xpath, but my xpath query is returning an empty list.  I need help in my xpath query. My python code and axml.xml are posted below.

========================= code =======================
tree = etree.parse("c:\\axml.xml")
rxpath = tree.xpath("//soap/soap/res/jx/fx/FA/Field/Length/text()")
print (rxpath)
 [ ]

============== axml.xml file ============
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
            <res xmlns="http://www.abcxp.com">
                  <jx xmlns="" xsi:type="gxen:output">
                        <fx xsi:type="name:Fields">
                              <FA xsi:type="name:ArrayOfField">
                                    <Field xsi:type="name:Field">
                                    <Field xsi:type="name:Field">

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1 Solution
Geert BormansInformation ArchitectCommented:
you have namespaces in your document,
so you need to bind the namespace to a prefix and prefix the lot



rxpath = tree.xpath("//soap:Envelope/soap:Body/abc:res/jx/fx/FA/Field/Length/text()", namespaces={'soap':  'http://schemas.xmlsoap.org/soap/envelope/', 'abc': 'http://www.abcxp.com'})
zeinthAuthor Commented:
awesome, it works in first attempt, thanks Gertone! for the xpath expression...

I have one last question here, from where this namespace key 'abc' is coming in the xpath

namespace = {'abc': 'http://www.abcxp.com'}

in xml file this namespace looks like, in the xpath expression I tried to use "xmlns" instead of 'abc' but it didn't work.

 <res xmlns="http://www.abcxp.com">
Geert BormansInformation ArchitectCommented:
ah, well xmlns="..." indicates the default namespace. It is teh namespace all elements have (below the declaration) that don't have a prefix
xmlns:abc="..." binds a prefix to a specific namespace
you can't tell etree that in teh xpath unprefixed elements are in a default namespace, so you need to bind the default namespace to a prefix

prefixes are a local pointer to a namespace. The namespace itself is important. So you can choose any prefix at any time, as long as it refers to the correct namespace

instead of
namespace = {'abc': 'http://www.abcxp.com'}
you could do
namespace = {'banana': 'http://www.abcxp.com'}
as long as you do then in the XPath
...("//soap:Envelope/soap:Body/banana:res ...
zeinthAuthor Commented:
thanks for explaining "prefixes are a local pointer to a namespace"
Geert BormansInformation ArchitectCommented:
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