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


xml源文件格式[例]

<?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> 

使用库:

xml.etree.ElementTree 

官方文档地址:http://docs.python.org/library/xml.etree.elementtree.html


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


代码附文档:

#!/usr/bin/python  
# -*- coding=utf-8 -*-  
# author : wklken@yeah.net  
# 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")