python中lxml的应用

首先下载lxml， http://www.lfd.uci.edu/~gohlke/pythonlibs/ ，然后添加引用

from lxml import _elementpath as DONTUSE

from lxml import etree

具体示例：

1.添加命名空间

#set namespace

nsmap = {"xsi": "http://www.w3.org/2001/XMLSchema-instance" }

g_statisticsRoot = etree.Element("DcmStatistics", nsmap = nsmap)

2.添加xml schema引用

#add xsd reference

g_statisticsRoot.set("{http://www.w3.org/2001/XMLSchema-instance}noNamespaceSchemaLocation", "DcmStatistics.xsd" )

3.添加注释

#add comment， 利用addprevious添加到根节点的前面

comment = etree.Comment("create by jiangong.li")

g_statisticsRoot.addprevious(comment)

4.尝试多种编码来解析xml

def decodingXml(xmlFile):

    tree = None

    encoding = "utf-8"

    while(True):

        try:

            parser = etree.XMLParser(remove_blank_text= True, encoding=encoding, remove_comments = False)

            tree = etree.parse(xmlFile, parser)

        except Exception as e:

            if (encoding != "gb18030"):

                encoding = "gb18030"

                continue

            else:

                print( "\nPAR XML ERROR, decoding error." )

                break

        break

    return tree

5.遍历xml下的所有子节点，不止直属第一级子节点. iter()

     for element in root.iter():

          element.tail = None

6.遍历xml下的第一级子节点. iterchildren()

    for e in srcParentNode.iterchildren():

        if e is srcParentNode:

            continue

        name = ""

        #statistics node

        if  e.tag == "element":

            name = "Element"

        elif e.tag == "sequence":

            name = "Sequence"

        elif e.tag == "item":

            name = "Item"

        else:

            print( "\nUnsupported element type: %s\n" %(e.tag))

            name = e.tag

            # Only parse element/sequence/item

             continue     

7.添加子节点到尾部. append()

def getXmlElement(nodeName, parentNode):

    if parentNode  == None:

        raise Exception( "parent node is None")

    nodes = parentNode.xpath( './'+nodeName)

    if len(nodes) == 0:

        node = etree.Element(nodeName)

        parentNode.append(node)

        return node

    else:

        return nodes[0]

8.格式化成str输出

etree.tostring(g_statisticsRoot, encoding= "UTF-8", xml_declaration=True , pretty_print=True, with_comments=True )

9.保存成xml文件

        statisticsResult =  open(g_xmlName, "bw+")

        statisticsResult.write(etree.tostring(g_statisticsRoot, encoding= "UTF-8", xml_declaration=True, pretty_print=True , with_comments=True))

        statisticsResult.flush()

        statisticsResult.close()