Python的Xpath介绍和语法详解

2023-02-17 20:25:40

1.简介

XPath是一门在XML和HTML文档中查找信息的语言,可以用来在XML和HTML文档中对元素和属性进行遍历

XPath的安装

Chrome插件XPath Helper

点Chrome浏览器右上角:更多工具-----扩展程序-----谷歌商店--------勾选XPath Helper(需要翻墙)

 

2.语法详解

 

#1.选取节点
'''
/   如果是在最前面,代表从根节点选取,否则选择某节点下的某个节点.只查询子一辈的节点
    /html   查询到一个结果
    /div    查询到0个结果,因为根节点以下只有一个html子节点
    /html/body  查询到1个结果

//  查询所有子孙节点
    //head/script
    //div

.   选取当前节点

..  选取当前节点的父节点

@   选取属性
    //div[@id]  选择所有带有id属性的div元素
    <div id="sidebar" class="sidebar" data-lg-tj-track-code="index_navigation" data-lg-tj-track-type="1">

'''
#2.谓语
'''
谓语是用来查找某个特定的节点或者包含某个指定的值的节点,被嵌在方括号中。
//body/div[1]                body下的第一个div元素
//body/div[last()]           body下的最后一个div元素
//body/div[position()<3]     body下的位置小于3的元素
//div[@id]                   div下带id属性的元素
<div id="sidebar" class="sidebar" data-lg-tj-track-code="index_navigation" data-lg-tj-track-type="1">
//input[@id="serverTime"]    input下id="serverTime"的元素

模糊匹配
//div[contains(@class,'f1')] div的class属性带有f1的
通配符 *
//body/*                    body下面所有的元素
//div[@*]                   只要有用属性的div元素
//div[@id='footer']    //div  带有id='footer'属性的div下的所有div元素
//div[@class='job_bt'] //dd[@class='job-advantage']

运算符
//div[@class='job_detail'] and @id='job_tent'
//book/title | //book/price         选取 book 元素的所有 title 和 price 元素。
也可以百度搜索XPath语法

.//a/text()         当前标签下所有a标签的文字内容
//tr[position()>1 and position()<11] 位置大于1小于11
'''

#需要注意的知识点
'''
1./和//的区别:/代表子节点,//代表子孙节点,//用的比较多
2.contains有时候某个属性中包含了多个值,那么使用contains函数
//div[contains(@class,'lg')]
3.谓语中的下标是从1开始的,不是从0开始的
'''

 

 

3.要在python中使用xpath,要导入一个库 lxml。

这个是C编写的库,直接pip3 install lxml可能会有一些显示问题,但是不影响使用。

然而程序员特有的代码洁癖让我看见波浪线也不会爽,所以去https://www.lfd.uci.edu/~gohlke/pythonlibs/下载lxml的whl文件进行pip(根据自己的pycharm版本选择)

 

4.lxml和xpath的结合使用

 

#  -*-coding:utf8 -*-
from lxml import etree
#1.获取所有tr标签
#2.获取第2个tr标签
#3.获取所有class等于even的标签
#4.获取所有a标签的href属性
#5.获取所有的职位信息(纯文本)



parser=etree.HTMLParser(encoding='utf-8')
html=etree.parse('tencent.html',parser=parser)

#1.获取所有tr标签
#xpath函数返回的是一个列表
# trs=html.xpath('//tr')
# print(trs)
# for tr in trs:
#     print(etree.tostring(tr,encoding='utf-8').decode('utf-8'))

#2.获取第2个tr标签

# trs=html.xpath('//tr[2]')[0]
#这样直接找第2个tr标签,实际上会把所有的table下的第二个tr标签找出来,
#为了更精准,可以先把table标签找到,再找这个table下的第二个tr标签
# trs=html.xpath('//table[@class="tablelist"]//tr[1]')[0]
# print(etree.tostring(trs,encoding='utf-8').decode('utf-8'))

#3.获取所有class等于even的标签
# trs=html.xpath("//tr[@class='even']")
# for tr in trs:
#     print(etree.tostring(tr, encoding='utf-8').decode('utf-8'))

#4.获取所有a标签的href属性
# a_list=html.xpath('//a/@href')
# for a in a_list:
#     print(a)

#5.获取所有的职位信息(纯文本)
trs=html.xpath('//tr[position()>1 and position()<11]')
positions=[]
for tr in trs:
    #写了//后,则一定会从整个文档找a标签,会无视前面的tr
    # href=tr.xpath('//a')
    #写了.后,则获取当前标签下的a标签
    href=tr.xpath('.//a/@href')[0]
    fullurl='http://hr.tencent.com/'+href
    #title文本信息不是td[1]的直接子元素标签,所以要加./td[1]//text()
    title=tr.xpath('./td[1]//text()')[0]
    category=tr.xpath('./td[2]/text()')[0]
    nums=tr.xpath('./td[3]/text()')[0]
    address=tr.xpath('./td[4]/text()')[0]
    pubtime=tr.xpath('./td[5]/text()')[0]
    position={
        'url':fullurl,
        'title':title,
        'category':category,
        'nums':nums,
        'pubtime':pubtime
    }
    positions.append(position)
# print(positions)

#6.获取纯文本信息还可以用string
# print(html.xpath("string(//tr[1])"))
# trs=html.xpath('//tr')
# for tr in trs:
    # print(tr.xpath("string(.)").strip()

 

 

5.实战案例,豆瓣电影爬虫

 

#  -*-coding:utf8 -*-
#1.将目标网站上的页面抓取下来
#2.将抓取下来的数据根据一定的规则进行提取

import requests
from lxml import etree
#1.将目标网站上的页面抓取下来
headers={
    'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36',
    'Referer':'https://www.douban.com/',
}
url='https://movie.douban.com/'
response=requests.get(url,headers=headers)
text=response.text
html=etree.HTML(text)
ul=html.xpath("//ul[@class='ui-slide-content']")[0]
# print(etree.tostring(ul,encoding='utf-8').decode('utf-8'))
lis=ul.xpath('./li[@data-title]')
movies=[]
for li in lis:
    title=li.xpath('@data-title')[0]
    score=li.xpath('@data-rate')[0]
    duration=li.xpath('@data-duration')[0]
    region=li.xpath('@data-region')[0]
    director=li.xpath('@data-director')[0]
    actors=li.xpath('@data-actors')[0]
    thumbnail=li.xpath('.//img/@src')[0]
    movie={
        'title':title,
        'score':score,
        'duration':duration,
        'region':region,
        'director':director,
        'actors':actors,
        'thumbnail':thumbnail
    }
    movies.append(movie)
print(movies)

 

 

6.实战案例,电影天堂爬虫

 

#  -*-coding:utf8 -*-
import requests
from lxml import etree

# url='https://www.dytt8.net/html/gndy/dyzz/list_23_1.html'
headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36'
}
# response=requests.get(url,headers=headers)
# 在电影天堂的网页中,因为编码方式,requests库猜错了,所以response.text出现乱码
# print(response.text)
# text=response.content.decode('gbk')
BaseDomain = 'https://www.dytt8.net'


def get_detail_url(url):
    response = requests.get(url, headers=headers)
    # print(response.encoding)
    # 默认解码方式ISO-8859-1
    # text=response.content.decode('gbk')
    # 在使用gbk解码时遇到了一些问题,第五页里有特殊字符,无法解析
    # 估计是因为xpath默认解码方式和gbk不一致导致的,这时可以直接传requests.text
    # 因为要获取的是英文字符,不指定解码方式也能得到
    html = etree.HTML(response.text)
    detail_urls = html.xpath('//table[@class="tbspan"]//a/@href')
    detail_urls = list(map(lambda url: BaseDomain + url, detail_urls))
    return detail_urls


def parse_detail_page(url):
    response = requests.get(url, headers=headers)
    text = response.content.decode('gbk')
    html = etree.HTML(text)
    title = html.xpath("//font[@color='#07519a' and position()=1]/text()")
    zoomE = html.xpath("//div[@id='Zoom']")[0]
    imgs = zoomE.xpath(".//img/@src")
    cover = imgs[0]
    screenshot = imgs[1]
    infos = zoomE.xpath(".//text()")
    movie = {
        'title': title,
        'cover': cover,
        'screenshot': screenshot
    }

    def parse_info(info, rule):
        return info.replace(rule, '').strip()

    for index, info in enumerate(infos):
        if info.startswith('◎年  代'):
            info = parse_info(info, '◎年  代')
            movie['year'] = info
        elif info.startswith('◎产  地'):
            info = parse_info(info, '◎产  地')
            movie['country'] = info
        elif info.startswith('◎类  别'):
            info = parse_info(info, '◎类  别')
            movie['category'] = info
        elif info.startswith('◎豆瓣评分'):
            info = parse_info(info, '◎豆瓣评分')
            movie['douban_rating'] = info
        elif info.startswith('◎片  长'):
            info = parse_info(info, '◎片  长')
            movie['duration'] = info
        elif info.startswith('◎导  演'):
            info = parse_info(info, '◎导  演')
            movie['director'] = info
        elif info.startswith('◎主  演'):
            info = parse_info(info, '◎主  演')
            actors = []
            actors.append(info)
            for x in range(index + 1, len(infos)):
                actor = infos[x].strip()
                if actor.startswith('◎简  介'):
                    break
                actors.append(actor)
            movie['actors'] = actors
        elif info.startswith('◎简  介 '):
            info=''
            for x in range(index+1,len(infos)):
                if infos[x].startswith('【下载地址】'):
                    break
                info = info + infos[x].strip()
            movie['profile']=info
    download_url = html.xpath("//td[@bgcolor='#fdfddf']//a/@href")[0]
    movie['download_url']=download_url
    return movie

def spider():
    # url = ['https://www.dytt8.net/html/gndy/dyzz/list_23_%s.html' % i for i in range(1, 8)]
    base_url = 'https://www.dytt8.net/html/gndy/dyzz/list_23_{}.html'
    movies=[]
    for x in range(1, 8):
        url = base_url.format(x)
        detail_urls = get_detail_url(url)
        for detail_url in detail_urls:
            movie = parse_detail_page(detail_url)
            movies.append(movie)
            print(movies)
if __name__ == '__main__':
    spider()

 

 

7.实战案例,腾讯招聘爬虫

 

#  -*-coding:utf8 -*-
import requests
from lxml import etree

base_url = 'https://hr.tencent.com/position.php?tid=87&start={}0#a'
base_domain = 'https://hr.tencent.com/'
headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36'
}
positions=[]

def parse_url(url):
    detail_urls=[]
    response=requests.get(url,headers=headers)
    html=etree.HTML(response.text)
    trs=html.xpath("//table[@class='tablelist']//tr[position()>1 and position()<12]")
    for tr in trs:
        href=tr.xpath('.//a/@href')[0]
        url=base_domain+href
        detail_urls.append(url)
    return detail_urls


def parse_detail_page(url):
    response=requests.get(url,headers=headers)
    html=etree.HTML(response.text)
    zoomE=html.xpath('//table[@class="tablelist textl"]')[0]
    title=zoomE.xpath('.//tr[1]/td/text()')[0]
    city=zoomE.xpath('.//tr[2]/td[1]/text()')[0]
    category=zoomE.xpath('.//tr[2]/td[2]/text()')[0]
    nums=zoomE.xpath('.//tr[2]/td[3]/text()')[0]
    duty=zoomE.xpath('.//tr[3]//ul//text()')
    dutys=''
    for i in duty:
        dutys=dutys+i.strip()
    require=zoomE.xpath('.//tr[4]//ul//text()')
    requires=''
    for i in require:
        requires=requires+i.strip()
    position={
        'title':title,
        'city':city,
        'category':category,
        'nums':nums,
        'dutys':dutys,
        'requires':requires
    }
    return position

if __name__ == '__main__':
    for i in range(1,10):
        url=base_url.format(i)
        detail_urls=parse_url(url)
        for detail_url in detail_urls:
            position=parse_detail_page(detail_url)
            positions.append(position)
            print(position)

 

  • 作者:Lansonli
  • 原文链接:https://lansonli.blog.csdn.net/article/details/104433926
    更新时间:2023-02-17 20:25:40