如何获取具有特定标签和属性的子元素的xml元素

Question

我想查找具有某些子元素的 xml 元素。子元素需要有一个给定的标签和一个设置为特定值的属性。

举一个具体的例子（基于official documentation）。我想找到所有具有neighbor 属性name="Austria" 的子元素的country 元素：

import xml.etree.ElementTree as ET

data = """<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <neighbor name="Malaysia" direction="N"/>
        <partner name="Austria"/>
    </country>
    <country name="Panama">
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>
"""

root = ET.fromstring(data)

我尝试过的没有成功：

countries1 = root.findall('.//country[neighbor@name="Austria"]')
countries2 = root.findall('.//country[neighbor][@name="Austria"]')
countries3 = root.findall('.//country[neighbor[@name="Austria"]]')

全部给出：

SyntaxError: 无效谓词

---

以下解决方案显然是错误的，因为发现的元素太多：

countries4 = root.findall('.//country/*[@name="Austria"]')
countries5 = root.findall('.//country/[neighbor]')

其中countries4 包含所有具有name="Austria" 属性的元素，但包括partner 元素。 countries5 包含所有具有 any 相邻元素作为子元素的元素。

Answer 1

import xml.etree.ElementTree as ET

data = """<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <neighbor name="Malaysia" direction="N"/>
        <partner name="Austria"/>
    </country>
    <country name="Panama">
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
    <country name="Liechtenstein">
        <neighbor name="Austria" direction="dummy"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    
</data>
"""

root = ET.fromstring(data)
for x in root.findall(".//country/neighbor[@name='Austria']"):
    print(x.attrib)

输出：

{'name': 'Austria', 'direction': 'E'}
{'name': 'Austria', 'direction': 'dummy'}

// : Selects all subelements, on all levels beneath the current element. For example, .//egg selects all egg elements in the entire tree.

[@attrib='value'] : Selects all elements for which the given attribute has the given value. The value cannot contain quotes

for x in root.find('.'):
    if x[0].attrib['name'] == 'Austria':
                   print(x.attrib['name']) 

输出： Liechtenstein

Answer 2

我想查找所有具有属性 name="Austria" 的子元素邻居的国家/地区元素

见下文

import xml.etree.ElementTree as ET

data = """<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <neighbor name="Malaysia" direction="N"/>
        <partner name="Austria"/>
    </country>
    <country name="Panama">
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>
"""

root = ET.fromstring(data)
countries_with_austria_as_neighbor = [c.attrib['name'] for c in root.findall('.//country') if
                                      'Austria' in [n.attrib['name'] for n in c.findall('neighbor')]]
print(countries_with_austria_as_neighbor)

输出

['Liechtenstein']