Python如何使用ElementTree解析xml
以country.xml為例,內容如下:
<?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)呼叫parse()方法，返回解析樹
try:
import xml.etree.cElementTree as ET
except ImportError:
import xml.etree.ElementTree as ET
tree = ET.parse("country.xml") # <class 'xml.etree.ElementTree.ElementTree'>
root = tree.getroot() # 獲取根節點 <Element 'data' at 0x02BF6A80>
2)呼叫from_string(),返回解析樹的根元素
import xml.etree.ElementTree as ET
data = open("country.xml").read()
root = ET.fromstring(data) # <Element 'data' at 0x036168A0>
3)呼叫ElementTree類ElementTree(self,element=None,file=None) # 這裡的element作為根節點
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>
1)簡單遍歷
import xml.etree.ElementTree as ET
tree = ET.parse("country.xml")
root = tree.getroot()
print(root.tag,":",root.attrib) # 列印根元素的tag和屬性
# 遍歷xml文件的第二層
for child in root:
# 第二層節點的標籤名稱和屬性
print(child.tag,child.attrib)
# 遍歷xml文件的第三層
for children in child:
# 第三層節點的標籤名稱和屬性
print(children.tag,children.attrib)
可以通過下標的方式直接訪問節點
# 訪問根節點下第一個country的第二個節點year,獲取對應的文字
year = root[0][1].text # 2008
2)ElementTree提供的方法
find(match) # 查詢第一個匹配的子元素， match可以時tag或是xpaht路徑
findall(match) # 返回所有匹配的子元素列表
findtext(match,default=None) #
iter(tag=None) # 以當前元素為根節點 建立樹迭代器,如果tag不為None,則以tag進行過濾
iterfind(match) #
例子:
# 過濾出所有neighbor標籤
for neighbor in root.iter("neighbor"):
print(neighbor.tag,neighbor.attrib)
# 遍歷所有的counry標籤
for country in root.findall("country"):
# 查詢country標籤下的第一個rank標籤
rank = country.find("rank").text
# 獲取country標籤的name屬性
name = country.get("name")
print(name,rank)
1) 屬性相關
# 將所有的rank值加1,並新增屬性updated為yes
for rank in root.iter("rank"):
new_rank = int(rank.text) + 1
rank.text = str(new_rank) # 必須將int轉為str
rank.set("updated","yes") # 新增屬性
# 再終端顯示整個xml
ET.dump(root)
# 注意 修改的內容存在記憶體中 尚未儲存到檔案中
# 儲存修改後的內容
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為屬性字典
# 刪除對應的屬性updated
del rank.attrib['updated']
ET.dump(root)
小結: 關於classxml.etree.ElementTree.Element 屬性相關
- attrib 為包含元素屬性的字典
- keys() 返回元素屬性名稱列表
- items() 返回(name,value)列表
- get(key,default=None) 獲取屬性
- set(key,value) # 跟新/新增 屬性
- del xxx.attrib[key] # 刪除對應的屬性
2) 節點/元素 相關
刪除子元素remove()
import xml.etree.ElementTree as ET
tree = ET.parse("country.xml")
root = tree.getroot()
# 刪除rank大於50的國家
for country in root.iter("country"):
rank = int(country.find("rank").text)
if rank > 50:
# remove()方法 刪除子元素
root.remove(country)
ET.dump(root)
新增子元素
程式碼:
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'
# 建立新的元素,tag為test_append
elem1 = ET.Element("test_append")
elem1.text = "elem 1"
# elem.tail = '\n\t'
country.append(elem1)
# SubElement() 其實內部呼叫的時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:
新增子元素方法總結:
- append(subelement)
- extend(subelements)
- insert(index,element)
4.建立xml文件
想建立root Element,然後建立SubElement,最後將root element傳入ElementTree(element),建立tree，呼叫tree.write()方法寫入檔案
對於建立元素的3個方法: 使用ET.Element、Element物件的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:
由於原生儲存的XML時預設無縮排，如果想要設定縮排的話， 需要修改儲存方式
程式碼:
import xml.etree.ElementTree as ET
from xml.dom import minidom
def 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,"Don't forget the meeting!")
# 儲存xml檔案
saveXML(root,"note.xml")
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