16 python xml模块

1、基本概念

xml是实现不同语言或程序之间进行数据交换的协议，跟json差不多，但json使用起来更简单。

不过，古时候，在json还没诞生的黑暗年代，大家只能选择用xml呀。

至今很多传统公司如金融行业的很多系统的接口还主要是xml。

xml的格式如下，就是通过<>节点来区别数据结构的:

<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year attr_test="yes">2009</year>
        <gdppc>141100</gdppc>
        <neighbor direction="E" name="Austria" />
        <neighbor direction="W" name="Switzerland" />
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year attr_test="yes">2012</year>
        <gdppc>59900</gdppc>
        <neighbor direction="N" name="Malaysia" />
    </country>
    <country name="Panama">
        <rank updated="yes">69</rank>
        <year attr_test="yes">2012</year>
        <gdppc>13600</gdppc>
        <neighbor direction="W" name="Costa Rica" />
        <neighbor direction="E" name="Colombia" />
    </country>
    <state>
        <name>德州</name>
        <population>德州</population>
    </state>
</data>

xml协议在各个语言里的都是支持的，在python中可以用以下模块操作xml

2、`遍历xml文档`

import xml.etree.ElementTree as ET
tree = ET.parse("xmltest.xml")
root = tree.getroot()#相当于f.seek(0)
print(root.tag)#输出最开始的date

#遍历xml文档
for child in root:
    print(child.tag, child.attrib
    for i in child:
        print(i.tag,i.text)
#------------------------------------------------------

---------- country {'name': 'Liechtenstein'}#child.tag,child.attrib
rank 2
year 2009
gdppc 141100#i.tag,i.text
neighbor None
neighbor None
---------- country {'name': 'Singapore'}
rank 5
year 2012
gdppc 59900
neighbor None
---------- country {'name': 'Panama'}
rank 69
year 2012
gdppc 13600
neighbor None
neighbor None
---------- state {}
name 德州
population 德州

#只遍历year 节点

for node in root.iter('year'):
    print(node.tag,node.text)
#-----------------------------------

year 2009
year 2012
year 2012

3、修改和删除xml文档内容

import xml.etree.ElementTree as ET
 
tree = ET.parse("xmltest.xml")
root = tree.getroot()
 
#修改
for node in root.iter('year'):
    new_year = int(node.text) + 1
    node.text = str(new_year)
    node.set("updated","yes")
 
tree.write("xmltest.xml")
 
#删除node
for country in root.findall('country'):
   rank = int(country.find('rank').text)
   if rank > 50:
     root.remove(country)
 
tree.write('output.xml')

4、自己创建xml文档

import xml.etree.ElementTree as ET
 
new_xml = ET.Element("namelist")
name = ET.SubElement(new_xml,"name",attrib={"enrolled":"yes"})
age = ET.SubElement(name,"age",attrib={"checked":"no"})
sex = ET.SubElement(name,"sex")
sex.text = ''
name2 = ET.SubElement(new_xml,"name",attrib={"enrolled":"no"})
age = ET.SubElement(name2,"age")
age.text = '
 
et = ET.ElementTree(new_xml) #生成文档对象
et.write("test.xml", encoding="utf-8",xml_declaration=True)
 
ET.dump(new_xml) #打印生成的格式