Python如何使用ElementTree解析xml

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\")

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持自学编程网。