xml模块

　　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。

一、xml格式如下，就是通过<>节点来区别数据结构的

 1 <?xml version="1.0"?>
 2 <data>
 3     <country name="Liechtenstein">
 4         <rank updated="yes">2</rank>
 5         <year>2008</year>
 6         <gdppc>141100</gdppc>
 7         <neighbor name="Austria" direction="E"/>
 8         <neighbor name="Switzerland" direction="W"/>
 9     </country>
10     <country name="Singapore">
11         <rank updated="yes">5</rank>
12         <year>2011</year>
13         <gdppc>59900</gdppc>
14         <neighbor name="Malaysia" direction="N"/>
15     </country>
16     <country name="Panama">
17         <rank updated="yes">69</rank>
18         <year>2011</year>
19         <gdppc>13600</gdppc>
20         <neighbor name="Costa Rica" direction="W"/>
21         <neighbor name="Colombia" direction="E"/>
22     </country>
23 </data>

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

1、遍历文档和节点

 1 import xml.etree.ElementTree as ET
 2 tree = ET.parse("xml test.xml")#打开xml文件
 3 root = tree.getroot()#f.seek
 4 print(root.tag)  # =>data，打印tag标签
 5 # 遍历xml文档
 6 for child in root:
 7     print(child.tag,child.attrib)
 8     for i in child:
 9         print(i.tag,i.text)
10 
11 # 只遍历year节点
12 for node in root.iter('year'):
13     print(node.tag,node.text)

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2、修改和删除xml的内容

 1 import xml.etree.ElementTree as ET
 2 tree = ET.parse("xml test.xml")
 3 root = tree.getroot()
 4 #修改
 5 for node in root.iter('year'):
 6     new_year = int(node.text)+1
 7     node.text = str(new_year)
 8     node.set("updated","yes")
 9 tree.write("xml test.xml")
10 
11 #删除
12 for country in root.findall("country"):
13     rank = int(country.find('rank').text)
14     if rank > 50:
15         root.remove(country)
16 tree.write("output.xml")

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3、自己创建xml文件

 1 #自己创建xml文档
 2 import xml.etree.ElementTree as ET
 3 new_xml = ET.Element("namelist")
 4 name = ET.SubElement(new_xml,"name",attrib={"enrolled":"yes"})
 5 age = ET.SubElement(name,"age",attrib={"checked":"no"})
 6 sex = ET.SubElement(name,"sex")
 7 sex.text = '33'
 8 name2 = ET.SubElement(new_xml,"name",attrib={"enrolled":"no"})
 9 age = ET.SubElement(name2,"age")
10 age.text = '19'
11 et = ET.ElementTree(new_xml) #生成文档对象
12 et.write("test.xml", encoding="utf-8",xml_declaration=True)
13 ET.dump(new_xml) #打印生成的格式

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