Python XPath 的常见问题与解决方法
- 如何解析XML文件?
使用Python内置的xml库，按照以下步骤进行解析：
1）导入xml.etree.ElementTree
import xml.etree.ElementTree as ET
2）使用parse函数将XML文件解析成一个ElementTree对象
tree = ET.parse('example.xml')
3）获取根节点
root = tree.getroot()
4）利用Element对象中的方法来获取节点，查找数据
for child in root:
print(child.tag, child.attrib)
具体例子如下：
Gambardella, Matthew
with XML.
Ralls, Kim
an evil sorceress, and her own childhood to become queen
of the world.
代码演示：
import xml.etree.ElementTree as ET
tree = ET.parse('example.xml')
root = tree.getroot()
for child in root:
print(child.tag, child.attrib)
输出结果：
book {'id': 'bk001'}
book {'id': 'bk002'}
- 如何使用XPath选取节点？
使用Python内置的xpath模块进行节点选取，步骤如下：
1）导入lxml库
from lxml import etree
2）将xml文件解析成一个Element对象
root = etree.parse('example.xml')
3）使用xpath函数进行选取
选取所有book节点
root.xpath('//book')
选取id为bk002的book的作者
root.xpath('//book[@id="bk002"]/author')
选取所有的author元素
root.xpath('//author')
具体例子如下：
Gambardella, Matthew
with XML.
Ralls, Kim
an evil sorceress, and her own childhood to become queen
of the world.
代码演示：
from lxml import etree
tree = etree.parse('example.xml')
选取所有的book节点
books = tree.xpath('//book')
for book in books:
print(book)
选取id为bk002的book的作者
author = tree.xpath('//book[@id="bk002"]/author')
print(author[0].text)
选取所有的author元素
authors = tree.xpath('//author')
for author in authors:
print(author.text)
输出结果：
Ralls, Kim
Gambardella, Matthew
Ralls, Kim
- 如何使用XPath选取属性？
使用Python内置的xpath模块进行属性选取，步骤如下：
1）导入lxml库
from lxml import etree
2）将xml文件解析成一个Element对象
root = etree.parse('example.xml')
3）选取属性
选取所有book的id属性
root.xpath('//book/@id')
选取id属性等于bk002的book的作者
root.xpath('//book[@id="bk002"]/author/text()')
具体例子如下：
Gambardella, Matthew
with XML.
Ralls, Kim
an evil sorceress, and her own childhood to become queen
of the world.
代码演示：
from lxml import etree
tree = etree.parse('example.xml')
选取所有book的id属性
ids = tree.xpath('//book/@id')
for id in ids:
print(id)
选取id属性等于bk002的book的作者
author = tree.xpath('//book[@id="bk002"]/author/text()')
print(author[0])
输出结果：
bk001
bk002
Ralls, Kim
- 如何使用xpath选取特定元素？
使用以下步骤：
1）使用xpath选取特定的元素
2）根据需要使用某些属性进行筛选
例如，选取所有book标签，并且其中的author标签的文本内容包含“Matthew”：
root.xpath('//book[author[contains(text(),"Matthew")]]')
具体例子如下：
Gambardella, Matthew
with XML.
Ralls, Kim
an evil sorceress, and her own childhood to become queen
of the world.
代码演示：
from lxml import etree
tree = etree.parse('example.xml')
选取所有book标签，并且其中的author标签的文本内容包含“Matthew”
books = tree.xpath('//book[author[contains(text(),"Matthew")]]')
for book in books:
print(book)
输出结果：
- 如何修改XML文档？
使用Python内置的xml.etree.ElementTree库中的Element对象的方法进行元素的修改：
1）修改元素text属性
elem.text = "new text"
2）修改元素attribute
elem.set("attrib", "new value")
3）修改元素tag
elem.tag = "new tag"
具体例子如下：
Gambardella, Matthew
with XML.
Ralls, Kim
an evil sorceress, and her own childhood to become queen
of the world.
代码演示：
import xml.etree.ElementTree as ET
tree = ET.parse('example.xml')
root = tree.getroot()
修改第一个book标签的作者
root[0].find('author').text = '皮蛋编程'
在第二个book标签下添加一本新书
new_book = ET.Element("book")
new_book.attrib["id"] = "bk003"
author = ET.SubElement(new_book, "author")
author.text = "pidancode.com"
title = ET.SubElement(new_book, "title")
title.text = "Python XPath tutorial"
genre = ET.SubElement(new_book, "genre")
genre.text = "Computer"
price = ET.SubElement(new_book, "price")
price.text = "9.99"
root[1].append(new_book)
tree.write('example.xml')
输出结果：
皮蛋编程
with XML.
Ralls, Kim
an evil sorceress, and her own childhood to become queen
of the world.
pidancode.com
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