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

python3.3之後ElementTree模組會自動尋找可用的C庫來加快速度

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>
 

2.遍歷

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)

3.修改xml結構

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class xml.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, 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!")

# 儲存xml檔案
saveXML(root, "note.xml")