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 ETexcept ImportError: import xml.etree.ElementTree as ETtree = 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 ETdata = 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 ETtree = 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 ETtree = 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yesfor 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xmlET.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 ETtree = 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 ETtree = 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 ETtree = ET.parse('country.xml')root = tree.getroot()country = root[0]last_ele = country[len(list(country))-1]last_ele.tail = ’ntt’# 创建新的元素, tag为test_appendelem1 = ET.Element('test_append')elem1.text = 'elem 1'# elem.tail = ’nt’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 ETdef 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 ETfrom xml.dom import minidomdef subElement(root, tag, text): ele = ET.SubElement(root, tag) ele.text = textdef 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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