标签:except 另一个 -- 小结 for 方法 default python head
Python标准库中,提供了ET的两种实现。一个是纯Python实现的xml.etree.ElementTree,另一个是速度更快的C语言实现xml.etree.cElementTree。请记住始终使用C语言实现,因为它的速度要快很多,而且内存消耗也要少很多。如果你所使用的Python版本中没有cElementTree所需的加速模块,你可以这样导入模块:
try:
import xml.etree.cElementTree as ET
except ImportError:
import xml.etree.ElementTree as ET
如果某个API存在不同的实现,上面是常见的导入方式。当然,很可能你直接导入第一个模块时,并不会出现问题。请注意,自Python 3.3之后,就不用采用上面的导入方法,因为ElemenTree模块会自动优先使用C加速器,如果不存在C实现,则会使用Python实现。因此,使用Python 3.3+的朋友,只需要import xml.etree.ElementTree即可。
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>
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>
本质上和方法三相同,parse() 源码如下:
def parse(source, parser=None):
"""Parse XML document into element tree.
*source* is a filename or file object containing XML data,
*parser* is an optional parser instance defaulting to XMLParser.
Return an ElementTree instance.
"""
tree = ElementTree()
tree.parse(source, parser)
return tree
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模块的 ElementTree(self, element=None, file=None)类 # 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>
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("\t" + 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("\t\t" + 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
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)
# 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class xml.etree.ElementTree.``Element 属性相关
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
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)
添加子元素方法总结:
? 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
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")
标签:except 另一个 -- 小结 for 方法 default python head
原文地址:https://www.cnblogs.com/dongye95/p/13974466.html