python模块之xml.etree.ElementTree

xml.etree.ElementTree用于解析和构建XML文件

<?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>

解析XML文件

parse()函数，从xml文件返回ElementTree

from xml.etree.ElementTree import parse
tree = parse('demo.xml')  //获取ElementTree
root = tree.getroot()   // 获取根元素

Element.tag 、Element.attrib、Element.text

In [6]: root.tag
Out[6]: 'data'

In [7]: root.attrib
Out[7]: {}

In [25]: root.text
Out[25]: '
    '

for child in root  迭代获得子元素

In [8]: for child in root:
   ...:     print(child.tag, child.attrib)
   ...:     
country {'name': 'Liechtenstein'}
country {'name': 'Singapore'}
country {'name': 'Panama'}

Element.get()  获得属性值

In [27]: for child in root:
    ...:     print (child.tag, child.get('name'))
    ...:     
country Liechtenstein
country Singapore
country Panama

root.getchildren()  获得直接子元素

In [21]: root.getchildren()
Out[21]: 
[<Element 'country' at 0x7f673581c728>,
 <Element 'country' at 0x7f673581ca98>,
 <Element 'country' at 0x7f673581cc28>]

root[0][1]  根据索引查找子元素

In [9]: root[0][1].text
Out[9]: '2008'

In [10]: root[1][0].text
Out[10]: '4'

root.find()　根据tag查找直接子元素，返回查到的第一个元素

In [13]: root.find('country').attrib
Out[13]: {'name': 'Liechtenstein'}

root.findall()    根据tag查找直接子元素，返回查到的所有元素的列表

In [16]: for country in root.findall('country'):
    ...:     print  (country.attrib)
    ...:     
{'name': 'Liechtenstein'}
{'name': 'Singapore'}
{'name': 'Panama'}

root.iterfind()   根据tag查找直接子元素，返回查到的所有元素的生成器

In [22]: root.iterfind('country')
Out[22]: <generator object prepare_child.<locals>.select at 0x7f6736dccfc0>　

支持的XPath语句(XML Path)

In [19]: root.findall('.//rank')  //查找任意层次元素
Out[19]: 
[<Element 'rank' at 0x7f673581c8b8>,
 <Element 'rank' at 0x7f673581c6d8>,
 <Element 'rank' at 0x7f673581cc78>]

In [32]: root.findall('country/*')  //查找孙子节点元素
Out[32]: 
[<Element 'rank' at 0x7f673581c8b8>,
 <Element 'year' at 0x7f673581cbd8>,
 <Element 'gdppc' at 0x7f673581c958>,
 <Element 'neighbor' at 0x7f673581c688>,
 <Element 'neighbor' at 0x7f673581cb38>,
 <Element 'rank' at 0x7f673581c6d8>,
 <Element 'year' at 0x7f673581c5e8>,
 <Element 'gdppc' at 0x7f673581c868>,
 <Element 'neighbor' at 0x7f673581cb88>,
 <Element 'rank' at 0x7f673581cc78>,
 <Element 'year' at 0x7f673581ccc8>,
 <Element 'gdppc' at 0x7f673581cd18>,
 <Element 'neighbor' at 0x7f673581cd68>,
 <Element 'neighbor' at 0x7f673581cdb8>]

In [33]: root.findall('.//rank/..')   // ..表示父元素
Out[33]: 
[<Element 'country' at 0x7f673581c728>,
 <Element 'country' at 0x7f673581ca98>,
 <Element 'country' at 0x7f673581cc28>]

In [34]: root.findall('country[@name]')   // 包含name属性的country
Out[34]: 
[<Element 'country' at 0x7f673581c728>,
 <Element 'country' at 0x7f673581ca98>,
 <Element 'country' at 0x7f673581cc28>]

In [35]: root.findall('country[@name="Singapore"]')   // name属性为Singapore的country
Out[35]: [<Element 'country' at 0x7f673581ca98>]

In [36]: root.findall('country[rank]')   // 孩子元素中包含rank的country
Out[36]: 
[<Element 'country' at 0x7f673581c728>,
 <Element 'country' at 0x7f673581ca98>,
 <Element 'country' at 0x7f673581cc28>]

In [37]: root.findall('country[rank="68"]')   // 孩子元素中包含rank且rank元素的text为68的country
Out[37]: [<Element 'country' at 0x7f673581cc28>]

In [38]: root.findall('country[1]')     // 第一个country
Out[38]: [<Element 'country' at 0x7f673581c728>]

In [39]: root.findall('country[last()]')   // 最后一个country
Out[39]: [<Element 'country' at 0x7f673581cc28>]

In [40]: root.findall('country[last()-1]')    // 倒数第二个country
Out[40]: [<Element 'country' at 0x7f673581ca98>]

root.iter()  递归查询指定的或所有子元素　

In [29]: root.iter()
Out[29]: <_elementtree._element_iterator at 0x7f67355dd728>

In [30]: list(root.iter())
Out[30]: 
[<Element 'data' at 0x7f673581c778>,
 <Element 'country' at 0x7f673581c728>,
 <Element 'rank' at 0x7f673581c8b8>,
 <Element 'year' at 0x7f673581cbd8>,
 <Element 'gdppc' at 0x7f673581c958>,
 <Element 'neighbor' at 0x7f673581c688>,
 <Element 'neighbor' at 0x7f673581cb38>,
 <Element 'country' at 0x7f673581ca98>,
 <Element 'rank' at 0x7f673581c6d8>,
 <Element 'year' at 0x7f673581c5e8>,
 <Element 'gdppc' at 0x7f673581c868>,
 <Element 'neighbor' at 0x7f673581cb88>,
 <Element 'country' at 0x7f673581cc28>,
 <Element 'rank' at 0x7f673581cc78>,
 <Element 'year' at 0x7f673581ccc8>,
 <Element 'gdppc' at 0x7f673581cd18>,
 <Element 'neighbor' at 0x7f673581cd68>,
 <Element 'neighbor' at 0x7f673581cdb8>]

In [31]: list(root.iter('rank'))
Out[31]: 
[<Element 'rank' at 0x7f673581c8b8>,
 <Element 'rank' at 0x7f673581c6d8>,
 <Element 'rank' at 0x7f673581cc78>]