How to search for a Xml node with a given attribut

问题:

I have this XML file and I want to get the country nodes which have the pattern 'in' in their name.

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank>1</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank>4</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank>68</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>

I have tried this

    import xml.etree.ElementTree as ET
    tree = ET.parse('test.xml')
    root = tree.getroot()
    list=root.find(".//country[contains(@name, 'Pana')]")

But I am getting an error : SyntaxError: invalid predicate

Could anyone please help how to solve this?

回答1:

xml.etree.ElementTree provides only limited support for XPath expressions for locating elements in a tree, and that doesn't include xpath contains() function. See the documentation for list of supported xpath syntax.

You need to resort to a library that provide better xpath support, like lxml, or use simpler xpath and do further filtering manually, for example :

import xml.etree.ElementTree as ET
tree = ET.parse('test.xml')
root = tree.getroot()
list = filter(lambda x: 'Pana' in x.get('name'), root.findall(".//country[@name]"))

回答2:

I cannot comment on why your original code does not work, but is has nothing to do with the XPath expression. The expression is fine, except for the leading . which you can safely omit.

Any reason you are not using the lxml xpath() method?

from lxml import etree
tree = etree.parse('etree.xml')
root = tree.getroot()
list = root.xpath("//country[contains(@name,'Pana')]")

print list[0].tag

gives back a country element:

$ python test.py
country

回答3:

The xml parser you are using does not support contains. You will need to use a different parser for full xpath support

https://docs.python.org/2/library/xml.etree.elementtree.html#elementtree-xpath