Python 基础

xml 模块介绍

和json一样，适用于不同语言及程序的数据交换的协议。但是json用起来更简单，并有代替xml的趋势。 现在多数金融数据提供方（e.g. bloombegy)还在用xml的方式。

在python中，生成和解析 XML 文件 用 导入 xml.etree.ElementTree 模块

xml文件的格式 

xml的格式如下，就是通过<>节点来区别数据结构的:

xml的格式

常用操作

读取xml

import xml.etree.ElementTree as ET

tree = ET.parse("xmltest.xml")
root = tree.getroot()
print(root.tag)  # 返回 data

# 历遍xml文档
for child in root:
    print(child.tag, child.attrib)   #返回country 层
    for i in child:
        print(i.tag, i.text)


# 只历遍year节点， 选择数据历遍
for node in root.iter("year"):
    print(node.tag,node.text)

修改删除xml文件内容

import xml.etree.ElementTree as ET

tree = ET.parse("xmltest.xml")
root = tree.getroot()

#修改数据
for node in root.iter("year"):
    new_year = int(node.text) + 1  # 每年都增加1
    node.text = str(new_year)   # 赋值
    node.set("updated","yes")   # 同时，修改attribution 属性

tree.write("xmltest.xml")


# 删除某个node
for country in root.findall("country"):
    rank = int(country.find('rank').text)
    if rank > 50:
        root.remove(country)

tree.write("output.xml")

创建新xml文件

import xml.etree.ElementTree as ET

new_xml = ET.Element("namelist")   # 创建根节点
personinfo = ET.SubElement(new_xml,"personinfo",attrib={"enrolled":"yea"})
name = ET.SubElement(personinfo,"name")
name.text = "alex li"
age = ET.SubElement(personinfo,"age",attrib={"checked":"no"})
age.text = "56"
sex = ET.SubElement(personinfo,"sex")
sex.text = "F"
personinfo2 = ET.SubElement(new_xml,"personinfo", attrib={"enrolled": "yes"})
name = ET.SubElement(personinfo2, "name")
name.text = "oldboy ran"
age = ET.SubElement(personinfo2, "age")
age.text = "22"

et = ET.ElementTree(new_xml)   # 生成文档对象
et.write("new_xml_test.xml", encoding="utf-8", xml_declaration=True)

ET.dump(new_xml) # 打印生成的格式