xml 模块
xml是时间不同语言或程序之间进行数据交换的协议,更json差不多,但是json使用起来更简单,不过xml诞生比较早,在json之前一般都用的xml,所以现在依然有些系统在用着xml,所以要学习xml的使用。
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>
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
import xml.etree.ElementTree as ET
tree = ET.parse("xmltest.xml")
root = tree.getroot()
print("顶级节点:", root.tag) # 打印出根节点的标签名为 data
for child in root:
print("-----子节点:", child.tag, child.attrib) # 获取到下一级子节点的标签名 和 属性, 如 country {'name': 'Liechtenstein'}
# 再进行一次遍历
for i in child:
print(i.tag, i.text) # 获取到再下一级的子节点的标签名 和 具体的值,如 rank 2
运行结果:
顶级节点: data -----子节点: country {'name': 'Liechtenstein'} rank 2 year 2008 gdppc 141100 neighbor None neighbor None -----子节点: country {'name': 'Singapore'} rank 5 year 2011 gdppc 59900 neighbor None -----子节点: country {'name': 'Panama'} rank 69 year 2011 gdppc 13600 neighbor None neighbor None
只遍历year节点:
import xml.etree.ElementTree as ET
tree = ET.parse("xmltest.xml")
root = tree.getroot()
# 只遍历 year节点
for year in root.iter("year"):
print(year.tag, year.text)
输出:
year 2008
year 2011
year 2011
修改和删除文档内容:
import xml.etree.ElementTree as ET
tree = ET.parse("xmltest.xml")
root = tree.getroot()
# 修改 ,给年+1
for node in root.iter("year"):
new_text = int(node.text) + 1
node.text = str(new_text)
node.set("updated", "yes") # 给year添加一个属性 updated
tree.write("xmltest.xml")
# 删除
for country in root.findall("country"):
rank = int(country.find("rank").text)
if rank > 50:
root.remove(country)
tree.write("output.xml")
自己创建xml文档:
import xml.etree.ElementTree as ET
new_xml = ET.Element("namelist") # 顶节点为 namelist
name = ET.SubElement(new_xml, "name", attrib={"enrolled": "yes"}) # 新建name节点,放到new_xml节点下,并声明属性 enrolled="yes"
age = ET.SubElement(name, "age", attrib={"checked": "no"}) # 新建 age 节点,放到 name节点下,并声明属性 checked="no"
sex = ET.SubElement(name, "sex") # 声明sex节点,放到name节点下
sex.text = "33" # 声明sex节点,值为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) # 写入文件,xml_declaration=True表示写入xml版本信息
ET.dump(new_xml) # 打印生成的格式
最终生成了文件 test.xml,内容为:
<?xml version='1.0' encoding='utf-8'?>
<namelist><name enrolled="yes"><age checked="no" /><sex>33</sex></name><name enrolled="no"><age>19</age></name></namelist>
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