Python怎样使用ElementTree解析xml

时间:2020-10-12 傻白甜++ 人气:0

以country.xml为例,内容如下:

<?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>

1.解析

1)调用parse()方法，返回解析树

try:
  import xml.etree.cElementTree as ET
except ImportError:
  import xml.etree.ElementTree as ET

tree = ET.parse("country.xml") # <class 'xml.etree.ElementTree.ElementTree'>
root = tree.getroot()      # 获取根节点 <Element 'data' at 0x02BF6A80>

2)调用from_string(),返回解析树的根元素

import xml.etree.ElementTree as ET
data = open("country.xml").read()
root = ET.fromstring(data) # <Element 'data' at 0x036168A0>

3)调用ElementTree类ElementTree(self, element=None, file=None) # 这里的element作为根节点

import xml.etree.ElementTree as ET
tree = ET.ElementTree(file="country.xml") # <xml.etree.ElementTree.ElementTree object at 0x03031390>
root = tree.getroot() # <Element 'data' at 0x030EA600>

1)简单遍历

import xml.etree.ElementTree as ET

tree = ET.parse("country.xml")
root = tree.getroot()
print(root.tag, ":", root.attrib) # 打印根元素的tag和属性
# 遍历xml文档的第二层
for child in root:
  # 第二层节点的标签名称和属性
  print(child.tag,":", child.attrib) 
  # 遍历xml文档的第三层
  for children in child:
    # 第三层节点的标签名称和属性
    print(children.tag, ":", children.attrib)

可以通过下标的方式直接访问节点

# 访问根节点下第一个country的第二个节点year,获取对应的文本
year = root[0][1].text # 2008

2)ElementTree提供的方法

find(match) # 查找第一个匹配的子元素， match可以时tag或是xpaht路径
findall(match) # 返回所有匹配的子元素列表
findtext(match, default=None) #
iter(tag=None) # 以当前元素为根节点创建树迭代器,如果tag不为None,则以tag进行过滤
iterfind(match) #

例子:

# 过滤出所有neighbor标签
for neighbor in root.iter("neighbor"):
print(neighbor.tag, ":", neighbor.attrib)

# 遍历所有的counry标签
for country in root.findall("country"):
# 查找country标签下的第一个rank标签
rank = country.find("rank").text
# 获取country标签的name属性
name = country.get("name")
print(name, rank)

1) 属性相关

# 将所有的rank值加1,并添加属性updated为yes
for rank in root.iter("rank"):
  new_rank = int(rank.text) + 1
  rank.text = str(new_rank) # 必须将int转为str
  rank.set("updated", "yes") # 添加属性

# 再终端显示整个xml
ET.dump(root)
# 注意 修改的内容存在内存中 尚未保存到文件中
# 保存修改后的内容
tree.write("output.xml")

import xml.etree.ElementTree as ET

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

for rank in root.iter("rank"):
  # attrib为属性字典
  # 删除对应的属性updated
  del rank.attrib['updated'] 

ET.dump(root)

小结: 关于classxml.etree.ElementTree.Element 属性相关

attrib 　　为包含元素属性的字典
keys() 返回元素属性名称列表
items() 返回(name,value)列表
get(key, default=None) 获取属性
set(key, value) # 跟新/添加属性
del xxx.attrib[key] # 删除对应的属性

2) 节点/元素相关

删除子元素remove()

import xml.etree.ElementTree as ET

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

# 删除rank大于50的国家
for country in root.iter("country"):
  rank = int(country.find("rank").text)
  if rank > 50:
    # remove()方法 删除子元素
    root.remove(country)

ET.dump(root)

添加子元素

代码:

import xml.etree.ElementTree as ET

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

country = root[0]
last_ele = country[len(list(country))-1]
last_ele.tail = '\n\t\t'
# 创建新的元素, tag为test_append
elem1 = ET.Element("test_append")
elem1.text = "elem 1"
# elem.tail = '\n\t'
country.append(elem1)

# SubElement() 其实内部调用的时append()
elem2 = ET.SubElement(country, "test_subelement")
elem2.text = "elem 2"

# extend()
elem3 = ET.Element("test_extend")
elem3.text = "elem 3"
elem4 = ET.Element("test_extend")
elem4.text = "elem 4"
country.extend([elem3, elem4])

# insert()
elem5 = ET.Element("test_insert")
elem5.text = "elem 5"
country.insert(5, elem5)

ET.dump(country)

效果:

添加子元素方法总结:

append(subelement)
extend(subelements)
insert(index, element)

4.创建xml文档

想创建root Element,然后创建SubElement,最后将root element传入ElementTree(element),创建tree，调用tree.write()方法写入文件

对于创建元素的3个方法: 使用ET.Element、Element对象的makeelement()方法以及ET.SubElement

import xml.etree.ElementTree as ET


def subElement(root, tag, text):
  ele = ET.SubElement(root, tag)
  ele.text = text
  ele.tail = '\n'


root = ET.Element("note")

to = root.makeelement("to", {})
to.text = "peter"
to.tail = '\n'
root.append(to)

subElement(root, "from", "marry")
subElement(root, "heading", "Reminder")
subElement(root, "body", "Don't forget the meeting!")

tree = ET.ElementTree(root)
tree.write("note.xml", encoding="utf-8", xml_declaration=True)

效果:

由于原生保存的XML时默认无缩进，如果想要设置缩进的话，需要修改保存方式

代码:

import xml.etree.ElementTree as ET
from xml.dom import minidom


def subElement(root, tag, text):
  ele = ET.SubElement(root, tag)
  ele.text = text


def saveXML(root, filename, indent="\t", newl="\n", encoding="utf-8"):
  rawText = ET.tostring(root)
  dom = minidom.parseString(rawText)
  with open(filename, 'w') as f:
    dom.writexml(f, "", indent, newl, encoding)
root = ET.Element("note")

to = root.makeelement("to", {})
to.text = "peter"
root.append(to)

subElement(root, "from", "marry")
subElement(root, "heading", "Reminder")
subElement(root, "body", "Don't forget the meeting!")

# 保存xml文件
saveXML(root, "note.xml")

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