本次示例使用python的lxml 对xpath进行演示
安装lxml
pip install lxml
xpath常规用法
示例html
htm = """"""
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
查找xxx下的所有xx元素
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath('//div/ul/li') # //代表从节结点开始查找,这里查找ul下为li的所有元素for i in all_li: print(i)执行结果:
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item# 0x1a7955a2808是内存地址,这是一组元素,如要显示具体可以这样(如:/a/text() # 查看a标签的文本(往下看也有演示))
查找xxx下的第一个xx元素
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath('//div/ul/li[1]') # 查找第一个li,注意在xpath中第一个下标不是0,而是1print(all_li)执行结果: [
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item]
注意:
如果网页中存在多个相同元素,不使用下标进行查找,系统只会默认查找第一个,若第一个元素不符会直接抛出异常。
查找xx元素对应的文本信息
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etree# all_li = selector.xpath('//div/ul/li[1]/a/text()')[0] # 这样写直接输出a下面的第一个文本all_li = selector.xpath('//div/ul/li[1]/a/text()') # 使用text()提取a标签下的文本信息print(all_li) # 也可以使用下标直接取出结果如:all_li[0]输出结果 first item执行结果: ['first item']
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
小知识
如果在使用的html页面中只要元素是唯一的,也可以不从根目录开始查找,简单示例几种:
all_li = selector.xpath('//ul/li[1]/a/text()')[0] #省去div一样可以all_li = selector.xpath('//*[@class="item-inactive"]/a/text()')[0] # 直接使用class查找第三个li的文本all_li = selector.xpath('//a[@href="link2.html"]/text()')[0] # 直接使用href查找第二个li的文本
获取xxx下元素的属性
获取单个属性
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath('//li[3]/a/@href')[0] # 获取href的属性print(all_li) 执行结果: link3.html
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
获取xxx对应的全部属性
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath('//li/@class') # 获取名称为class的全部属性print(all_li)执行结果: ['item-0', 'item-1', 'item-inactive', 'item-1', 'item-0', 'else-1']
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
xpath高级用法
查找出xxx元素以xx开头的属性
还是这段html来做演示:
"""
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
使用starts-with()
示例代码:
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath("//li[starts-with(@class, 'item-')]") # 获取href的属性all_a = []for i in all_li: all_a.append(i.xpath('a/text()')[0]) # 继续对找到的li元素使用xpath查找其里面的内容print(all_a)执行结果: ['first item', 'second item', 'third item', 'fourth item', 'fifth item']
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
也可以这样写:
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath("//li[starts-with(@class, 'item-')]/a/text()") # 获取href的属性print(all_li)执行结果: ['first item', 'second item', 'third item', 'fourth item', 'fifth item']
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
查找所有文本
使用string()
示例代码:
from lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)htm = """"""selector = etree.HTML(htm) # 初始化etreeall_li = selector.xpath("string(//ul)") # 获取ul下的所有文本print(all_li)执行结果: first item second item third item fourth item fifth item something else this is ul item
- first item
- second item
- third item
- fourth item
- fifth item
- something else
this is ul item
小小实例
获取豆瓣首页的豆瓣读书文本及链接,在首页取出一张图片存入本地。
import requestsfrom lxml import etree # 在pycharm中遇到红线提示找不到etree的初始化方法,没关系不影响(File → settings → project → project interpreter重新加载一下即可)r = requests.get('https://www.douban.com/')r.encoding = 'utf-8'html = etree.HTML(r.text)text = html.xpath('//*[@id="anony-nav"]/div[1]/ul/li[1]/a/@href')[0]h1 = html.xpath('//*[@id="anony-nav"]/div[1]/ul/li[1]/a/text()')[0]logs = html.xpath('//*[@id="anony-sns"]/div/div[3]/div/div[1]/ul/li[3]/div/a/img/@src')[0]print(text)print(h1)print(logs)log = requests.get(logs)with open('d:/a.gif', 'wb') as file: # wb 二进制形式写入 file.write(log.content) # 保存图片执行结果: https://book.douban.com 豆瓣读书 https://img3.doubanio.com/f/shire/a1fdee122b95748d81cee426d717c05b5174fe96/pics/blank.gif