详解在Python程序中解析并修改XML内容的方法

需求
在实际应用中，需要对xml配置文件进行实时修改，

1.增加、删除 某些节点

2.增加，删除，修改某个节点下的某些属性

3.增加，删除，修改某些节点的文本

使用xml文档

<?xml version="1.0" encoding="UTF-8"?>
<framework>
  <processers>
    <processer name="AProcesser" file="lib64/A.so"
      path="/tmp">
    </processer>
    <processer name="BProcesser" file="lib64/B.so" value="fordelete">
    </processer>
    <processer name="BProcesser" file="lib64/B.so2222222"/>

    <services>
      <service name="search" prefix="/bin/search?"
        output_formatter="OutPutFormatter:service_inc">

        <chain sequency="chain1"/>
        <chain sequency="chain2"></chain>
      </service>
      <service name="update" prefix="/bin/update?">
        <chain sequency="chain3" value="fordelete"/>
      </service>
    </services>
  </processers>
</framework>

实现思想
使用ElementTree，先将文件读入，解析成树，之后，根据路径，可以定位到树的每个节点，再对节点进行修改，最后直接将其输出

实现代码

#!/usr/bin/python
# -*- coding=utf-8 -*-
# author : [e-mail]
# date: 2012-05-25
# version: 0.1

from xml.etree.ElementTree import ElementTree,Element

def read_xml(in_path):
  '''读取并解析xml文件
    in_path: xml路径
    return: ElementTree'''
  tree = ElementTree()
  tree.parse(in_path)
  return tree

def write_xml(tree, out_path):
  '''将xml文件写出
    tree: xml树
    out_path: 写出路径'''
  tree.write(out_path, encoding="utf-8",xml_declaration=True)

def if_match(node, kv_map):
  '''判断某个节点是否包含所有传入参数属性
    node: 节点
    kv_map: 属性及属性值组成的map'''
  for key in kv_map:
    if node.get(key) != kv_map.get(key):
      return False
  return True

#---------------search -----
def find_nodes(tree, path):
  '''查找某个路径匹配的所有节点
    tree: xml树
    path: 节点路径'''
  return tree.findall(path)

def get_node_by_keyvalue(nodelist, kv_map):
  '''根据属性及属性值定位符合的节点，返回节点
    nodelist: 节点列表
    kv_map: 匹配属性及属性值map'''
  result_nodes = []
  for node in nodelist:
    if if_match(node, kv_map):
      result_nodes.append(node)
  return result_nodes

#---------------change -----
def change_node_properties(nodelist, kv_map, is_delete=False):
  '''修改/增加 /删除 节点的属性及属性值
    nodelist: 节点列表
    kv_map:属性及属性值map'''
  for node in nodelist:
    for key in kv_map:
      if is_delete:
        if key in node.attrib:
          del node.attrib[key]
      else:
        node.set(key, kv_map.get(key))

def change_node_text(nodelist, text, is_add=False, is_delete=False):
  '''改变/增加/删除一个节点的文本
    nodelist:节点列表
    text : 更新后的文本'''
  for node in nodelist:
    if is_add:
      node.text += text
    elif is_delete:
      node.text = ""
    else:
      node.text = text

def create_node(tag, property_map, content):
  '''新造一个节点
    tag:节点标签
    property_map:属性及属性值map
    content: 节点闭合标签里的文本内容
    return 新节点'''
  element = Element(tag, property_map)
  element.text = content
  return element

def add_child_node(nodelist, element):
  '''给一个节点添加子节点
    nodelist: 节点列表
    element: 子节点'''
  for node in nodelist:
    node.append(element)

def del_node_by_tagkeyvalue(nodelist, tag, kv_map):
  '''同过属性及属性值定位一个节点，并删除之
    nodelist: 父节点列表
    tag:子节点标签
    kv_map: 属性及属性值列表'''
  for parent_node in nodelist:
    children = parent_node.getchildren()
    for child in children:
      if child.tag == tag and if_match(child, kv_map):
        parent_node.remove(child)

if __name__ == "__main__":
  #1. 读取xml文件
  tree = read_xml("./test.xml")

  #2. 属性修改
   #A. 找到父节点
  nodes = find_nodes(tree, "processers/processer")
   #B. 通过属性准确定位子节点
  result_nodes = get_node_by_keyvalue(nodes, {"name":"BProcesser"})
   #C. 修改节点属性
  change_node_properties(result_nodes, {"age": "1"})
   #D. 删除节点属性
  change_node_properties(result_nodes, {"value":""}, True)

  #3. 节点修改
   #A.新建节点
  a = create_node("person", {"age":"15","money":"200000"}, "this is the firest content")
   #B.插入到父节点之下
  add_child_node(result_nodes, a)

  #4. 删除节点
    #定位父节点
  del_parent_nodes = find_nodes(tree, "processers/services/service")
    #准确定位子节点并删除之
  target_del_node = del_node_by_tagkeyvalue(del_parent_nodes, "chain", {"sequency" : "chain1"})

  #5. 修改节点文本
    #定位节点
  text_nodes = get_node_by_keyvalue(find_nodes(tree, "processers/services/service/chain"), {"sequency":"chain3"})
  change_node_text(text_nodes, "new text")

  #6. 输出到结果文件
  write_xml(tree, "./out.xml")

修改后的结果

<?xml version='1.0' encoding='utf-8'?>
<framework>
  <processers>
    <processer file="lib64/A.so" name="AProcesser" path="/tmp">
    </processer>
    <processer age="1" file="lib64/B.so" name="BProcesser">
      <person age="15" money="200000">this is the firest content</person>
    </processer>
    <processer age="1" file="lib64/B.so2222222" name="BProcesser">
      <person age="15" money="200000">this is the firest content</person>
    </processer>

    <services>
      <service name="search" output_formatter="OutPutFormatter:service_inc"
        prefix="/bin/search?">

        <chain sequency="chain2" />
      </service>
      <service name="update" prefix="/bin/update?">
        <chain sequency="chain3" value="fordelete">new text</chain>
      </service>
    </services>
  </processers>
</framework>