python3之xml处理(xml.etree.ElementTree)

  • XML简介
    XML(可扩展性标记语言eXtensible Markup Language)是一种非常常用的文件类型,被设计用来传输和存储数据而不是显示数据(HTML用于显示数据),XML 标签没有被预定义。您需要自行定义标签。python3.3以后使用xml.etree.ElementTree模块。
  • XML格式
    (1)标签/元素
    (2)属性
    (3)数据
    例如:

<breakfast_menu>
    <food>
        <name>Belgian Wafflesname>
        <price>$5.95price>
        <description>
            Two of our famous Belgian Waffles with plenty of real maple syrup
        description>
        <calories>650calories>
    food>
    <food>
        <name>Strawberry Belgian Wafflesname>
        <price>$7.95price>
        <description>
            Light Belgian waffles covered with strawberries and whipped cream
        description>
        <calories>900calories>
        food>
breakfast_menu>
  • XML读取操作
    有以下两种方式可以对XML字符串进行操作,都是拿到根节点breakfast_menu元素,在此基础上增删改查XML
    (1)通过字符串方式读取,参数为XML字符串,直接返回的是一个根Element对象
import xml.etree.ElementTree as ET
xml_string ='''

    
        Belgian Waffles
        $5.95
        
            Two of our famous Belgian Waffles with plenty of real maple syrup
        
        650
    
    
        Strawberry Belgian Waffles
        $7.95
        
            Light Belgian waffles covered with strawberries and whipped cream
        
        900
        
    
        Berry-Berry Belgian Waffles
        $8.95
        Light Belgian waffles covered with an assortment of fresh berries and whipped cream
        900
    
    
        French Toast
        $4.50
        
            Thick slices made from our homemade sourdough bread
        
        600
    
    
        Homestyle Breakfast
        $6.95
        
            Two eggs, bacon or sausage, toast, and our ever-popular hash browns
        
        950
    

'''
root = ET.fromstring(xml_string)
print(root) ==> <Element 'breakfast_menu' at 0x101f94a98>

(2)从xml文件中读取,用getroot获取根节点,根节点也是Element对象

import xml.etree.ElementTree as ET
tree = ET.parse('xml_test')
root = tree.getroot()
print(tree) ==> <xml.etree.ElementTree.ElementTree object at 0x104100a20>
print(root) ==> <Element 'breakfast_menu' at 0x101d94a98>这个通第一种方式直接获取的结果一样
  • 访问XML元素:标签(tag)、属性(attrib)、值(text)
    (1)访问Element元素对象的标签、属性、值
tag = element.tag
attrib = element.attrib # 字典
value = element.text

(2)访问子节点元素对象及其标签、属性、值

# 这里的for i in root只能访问root的直接子元素,下面的for I in root.iter()是访问直接子元素。
for child in root:
    print(child,child.tag,child.attrib,child.text)
    for child_child in child:
        print(child_child, child_child.tag, child_child.attrib, child_child.text)

#结果类似如下:

<Element 'food' at 0x101e94bd8> food {} 
        <Element 'name' at 0x104111cc8> name {} Belgian Waffles<Element 'price' at                   0x104570278> price {} $5.95
        <Element 'description' at 0x1045702c8> description {} 
                  Two of our famous Belgian Waffles with plenty of real maple syrup
		<Element 'calories' at 0x104570908> calories {} 650
		
<Element 'food' at 0x10457a9f8> food {} 
        <Element 'name' at 0x10457aa48> name {} Strawberry Belgian Waffles
		<Element 'description' at 0x10457ab38> description {} 
                  Light Belgian waffles covered with strawberries and whipped cream
        <Element 'calories' at 0x10457ab88> calories {} 900
        
        

(3)Elements元素对象都是可迭代的对象,可以直接对其list(Element)将其转化为列表或者直接索引取:

import xml.etree.ElementTree as ET
tree = ET.parse('xml_test')
root = tree.getroot()
print(list(root)) ==>[<Element 'food' at 0x101c94bd8>, <Element 'food' at 0x10457aa48>, <Element 'food' at 0x10457ac28>, <Element 'food' at 0x10457ae08>, <Element 'food' at 0x10457af98>]
print(root[0],root[1])

如上,list(root)的结果就是其3个子元素组成的列表,这时可以访问其标签、属性、值,然后对其每个子元素也可以同样的方法转换为列表访问各个属性,当然可以通过迭代的方法用for循环来操作。

(4)按照元素名字访问或者迭代元素

 1. Element.iter("tag"),可以罗列该节点所包含的所有其他节点(element对象)
	print(root.iter()) :返回一个可迭代对象,迭代这个对象可以迭代出包括根节点在内的所有元素节点
	print(list(root.iter())) :返回一个列表,将所有元素对象放在一个列表中
	print(root.iter('name')) :返回一个可迭代对象,迭代这个对象可以迭代出所有元素标签名为name的元素elemen对象
	print(list(root.iter('name'))):返回一个列表,将所有标签名为name的元素对象放到一个列表中
 2. Element.findall("tag"):查找当前元素为“tag”的直接子元素,tag不能省略
 3. Element.find("tag"):查找为tag的第一个直接子元素,如没有,返回None

(5)修改XML文件

ElementTree.write("xml_test"):更新xml文件
Element.append(element):为当前element对象添加子元素(element)
Element.set(key,value):为当前element的key属性设置value值
Element.remove(element):删除为element的节点
#读取待修改xml文件
updateTree = ET.parse("xml_test")
root = updateTree.getroot()
#创建新节点并添加为root的子节点
newEle = ET.Element("NewElement")
newEle.attrib = {"name":"NewElement","age":"20"}
newEle.text = "This is a new element"
root.append(newEle)

#修改sub1的name属性
sub1 = root.find("food")
sub1.set("name","New Name")

#修改sub2的数据值
sub2 = root.find("sub2")
sub2.text = "New Value"

#写回原文件
updateTree.write("xml_test")

# sample.xml
<data data_attrib="hello xml" data_attrib2="hello xml2">
    <country name="Liechtenstein">
        <rank>1rank>
        <year>2008year>
        <gdppc>141100gdppc>
        <neighbor direction="E" name="Austria">textqqqneighbor>
        <neighbor direction="W" name="Switzerland" />
    country>
    <country name="Singapore">
        <rank>4rank>
        <year>2011year>
        <gdppc>59900gdppc>
        <neighbor direction="N" name="Malaysia" />
    country>
    <country name="Panama">
        <rank>68rank>
        <year>2012year>
        <gdppc>13600gdppc>
        <neighbor direction="W" name="Costa Rica" />
        <neighbor direction="E" name="Colombia" />
    country>
    <country name="China">
        <rank>8rank>
        <neighbor direction="E" name="Japan">I am Japanneighbor>
    country>
data>
tree = ElementTree.parse('sample.xml')
root = tree.getroot()
for country in root.findall('country'):
    if country.attrib["name"] == "China":
        neighbor = country.find("neighbor")
        neighbor.text = "I am Japan"
        tree.write('sample.xml')

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