xml模块（了解）

3 xml模块（了解）

1 很久以前，前后端交互，使用xml格式（前端是html格式）
2 现在主流都用json
    <title>百度一下，你就知道</title>
    {'title':'百度一下，你就知道'}

3.1、xml简介

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。

xmltest.xml

xml的格式如下，就是通过<>节点来区别数据结构的:

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank updated="yes">69</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>

3.2、Python使用xml

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：

# print(root.iter('year')) #全文搜索
# print(root.find('country')) #在root的子节点找，只找一个
# print(root.findall('country')) #在root的子节点找，找所有

import xml.etree.ElementTree as ET

tree = ET.parse("xmltest.xml")
root = tree.getroot()
print(root.tag)  # data  读取到xmltest.xml文件的标签是data。

#遍历xml文档
for child in root:
    """遍历根元素root打印出====>country {'name': 'Liechtenstein'} Liechtenstein"""
    print('====>', child.tag, child.attrib, child.attrib['name'])
    for i in child:
        print(i.tag, i.attrib, i.text)
"""
rank {'updated': 'yes'} 2
year {} 2008
gdppc {} 141100
neighbor {'name': 'Austria', 'direction': 'E'} None
neighbor {'name': 'Switzerland', 'direction': 'W'} None
.....
"""

# #只遍历year 节点
for node in root.iter('year'):
    print(node.tag, node.text)
"""输出:
year 2008
year 2011
year 2011"""
# #---------------------------------------
#
# 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')
#     node.set('version', '1.0')
# tree.write('test.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')
#
# #在country内添加（append）节点year2
# import xml.etree.ElementTree as ET
# tree = ET.parse("a.xml")
# root = tree.getroot()
# for country in root.findall('country'):
#     for year in country.findall('year'):
#         if int(year.text) > 2000:
#             year2 = ET.Element('year2')
#             year2.text = '新年'
#             year2.attrib = {'update': 'yes'}
#             country.append(year2)  #往country节点下添加子节点
#
# tree.write('a.xml.swap')

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 = '33'
name2 = ET.SubElement(new_xml,"name",attrib={"enrolled":"no"})
age = ET.SubElement(name2,"age")
age.text = '19'
 
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