1.xpath语法

xpath语法

2.1用lxml库解析html字符串和文件

from lxml import etree
#解析HTML字符串
html = etree.HTML(text)
print(etree.tostring(html,encoding="utf-8").decode("utf-8"))
#解析HTML文件
html = etree.HTML("lagou.html")
print(etree.tostring(html,encoding="utf-8").decode("utf-8"))
#解析HTML文件错误时（默认为xml解析器）需创建指定的解析器
parser = etree.HTMLParser(encoding = 'utf-8')
html = etree.HTML("lagou.html",parser=parser)
print(etree.tostring(html,encoding="utf-8").decode("utf-8"))

2.2xpath和lxml库配合使用

from lxml import etree
parser = etree.HTMLParser(encoding = "utf-8")
html = etree.parse('tencet.html',parser = parser)
#1.获取所有tr标签
trs = html.xpath("//tr") #xpath返回的是个列表
for tr in trs:
    print(etree.tostring(tr,encoding='utf-8').decode("utf-8"))
#2.获取第二个tr标签
tr = html.xpath("//tr[2]").[0]
print(etree.tostring(tr,encoding='utf-8').decode("utf-8"))
#3.获取所有class = even得tr标签
tr = html.xpath("//tr[@clss = 'even']")
#4.获取所有a标签的href属性
alist = html.xpath("//a/@herf")
#5.获取某个标签下的文本文档
title = tr.xpath(".//td[1]//text()")

示例 电影天堂爬取

import requests
from lxml import etree
Base_DOMAIN = 'https://www.dytt8.net/'
# 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/83.0.4103.61 Safari/537.36",
    "Referer": "https://www.dytt8.net/html/gndy/dyzz/list_23_2.html"}


def get_url(url):
    resp = requests.get(url, headers=HEADERS)
    # text = resp.content.decode('gbk', errors='ignore')
    text = resp.text
    html = etree.HTML(text)
    links = html.xpath("//table[@class='tbspan']//a/@href")
    urls = map(lambda url: Base_DOMAIN + url, links)
    return urls


def jx(url):
    movies = {}
    resp = requests.get(url, headers=HEADERS)
    text = resp.content.decode('gbk', errors='ignore')
    html = etree.HTML(text)
    movie_title = html.xpath(
        "//div[@class='title_all']//font[@color='#07519a']/text()")[0]
    movies["title"] = movie_title
    Zoom = html.xpath("//div[@id='Zoom']")[0]
    photos = Zoom.xpath(".//img/@src")
    haibao = photos[0]
    movies["haibao"] = haibao
    infos = Zoom.xpath(".//text()")
    for index, info in enumerate(
            infos):  # enumerate(infos)返回两个值，下标和内容，获取演员列表需要下标
        if info.startswith(
                "◎年　　代"):  # startswith("text")查找以text为开头的部分，并返回text整体
            # info = info.replace("◎年　　代","").strip()
            # #replace()将text整体中text部分替换为空，即去除text部分,strip()去掉内容前后空格
            year = info_1(info, "◎年　　代")
            movies["years"] = year
        elif info.startswith("◎豆瓣评分"):
            # info = info.replace("◎豆瓣评分","").strip()
            scores = info_1(info, "◎豆瓣评分")
            movies["scores"] = scores
        elif info.startswith("◎主　　演"):
            info = info_1(info, "◎主　　演")
            actor = [info]
            for x in range(index + 1, len(infos)):
                actors = infos[x].strip()
                if actors.startswith("◎"):
                    break
                actor.append(actors)
            movies["actors"] = actor
        elif info.startswith("◎简　　介"):
            info = info_1(info, "◎简　　介")
            for x in range(index + 1, len(infos)):
                profile = infos[x].strip()
                if profile.startswith("◎"):
                    break
                movies["profile"] = profile
    download_url = html.xpath("//td[@bgcolor='#fdfddf']/a/@href")
    movies["download_url"] = download_url
    return movies


def info_1(info, rule):
    return info.replace(rule, "").strip()


def spider():
    base_url = 'https://www.dytt8.net/html/gndy/dyzz/list_23_{}.html'  # 预留页码位置
    film = []
    for x in range(1, 2):
        url = base_url.format(x)  # 填入页码位置获得完整链接
        films_details = get_url(url)
        for page_url in films_details:
            movie = jx(page_url)
            film.append(movie)
            print(film)
    # with open("E:/桌面/电影.txt","w")as f:
    #     for x in film:
    #         f.write("\n"+str(x))



if __name__ == '__main__':
    spider()

3.BeautifulSoup4库

BeautifulSoup也是HTML/XML的解析器，主要用于解析和提取HTML/XML。它作用于HTML DOM，会载入整个文档，而xpath只是局部遍历，因此BeautifulSoup性能上低于xpath，但它解析HTML比xpath简单
安装方法：pip安装

pip install bs4

基本使用

from bs4 import BeautifulSoup
bs = BeautifulSoup(html,'lxml')#将HTML导入用lxml解析器进行解析
#1.获取所有tr标签
trs = soup.find_all('tr')
#2.获取第二个tr标签
tr_2 = soup.find_all('tr',limit=2)[1] #limit限制获取几个数据，find_all返回列表
#3.获取所有class=even的标签
tr_even = soup.find_all('tr',class_='even')
tr_even = soup.find_all('tr',attrs={'class':'even'})#atrrs可指定获取tr的某些属性
#4.获取id=test，class=test的a标签
alist = soup.find_all('a',id='test',class_='test')
alist = soup.find_all('a',attrs={'id':'test','class':'test'})
#5.获取a标签下的href属性
alist = soup.find_all('a')
for a in alist:
    #方法1
    href = a['href']
    #方法2
    href = a.attrs('href')
#6.获取所有文本
tr_3 = soup.find_all('tr')[1:]#过滤第一个
for tr in tr_3:
    #infos = tr.strings #用strings会包括“\n”等字符,string会返回字符串，get_text()返回的不是列表
    infos = tr.stripped_strings#获取非空字符
    infos =list(infos) #转换为列表可提取其中元素

CSS选择器 select

#1.通过标签名查找
print(soup.select('a'))
#2.通过类名查找，如查找class=sy
print(soup.select('.sy'))
#3.通过id查找
print(soup.select('#sy'))
#4.组合查找 标签+id/class等
print(soup.select('p #sy'))
#5.通过属性查找
print(soup.select("a[href='http://......']"))

实例

#BeautifulSoup实例及数据可视化简单应用
import requests
from bs4 import BeautifulSoup
from pyecharts.charts import Bar #数据可视化库，版本1.7.1，新版本改动
from pyecharts import options as opts

weather = []
def page_parse(url):
    headers = {
        'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36'
    }
    resp = requests.get(url,headers=headers).content.decode('utf-8')
    soup = BeautifulSoup(resp,'html5lib') #港澳台地区需要用html5lib进行解析
    conmidtabs = soup.find('div',class_='conMidtab')
    tables = conmidtabs.find_all('table')
    for table in tables:
        trs = table.find_all('tr')[2:]
        for index,tr in enumerate(trs):
            tds = tr.find_all('td')
            city_td = tds[0]
            if index == 0:
                city_td = tds[1]
            city = list(city_td.stripped_strings)[0]
            temp_td = tds[-2]
            temp = list(temp_td.stripped_strings)[0]
            # print({'city':city,'min-temp':temp})
            weather.append({'city':city,'min_temp':int(temp)})
    # with open('E:/桌面/weather.txt','w')as fp:
    #     for x in weather:
    #         fp.write('\n'+str(x))


def main():
    urls = [
        'http://www.weather.com.cn/textFC/hb.shtml',
        'http://www.weather.com.cn/textFC/db.shtml',
        'http://www.weather.com.cn/textFC/hd.shtml',
        'http://www.weather.com.cn/textFC/hz.shtml',
        'http://www.weather.com.cn/textFC/hn.shtml',
        'http://www.weather.com.cn/textFC/xb.shtml',
        'http://www.weather.com.cn/textFC/xn.shtml',
        'http://www.weather.com.cn/textFC/gat.shtml'
    ]
    for url in urls:
        page_parse(url)
    weather.sort(key=lambda weather:weather['min_temp'])
    data = weather[0:10]
    # print(data)
    cities = list(map(lambda x:x['city'],data))
    min_temps = list(map(lambda x:x['min_temp'],data))
    chart = Bar() #创建一个直方图
    chart.set_global_opts(title_opts=opts.TitleOpts(title="天气预报")) #创建直方图主标题
    chart.add_xaxis(cities)
    chart.add_yaxis('',min_temps)
    chart.set_global_opts(xaxis_opts=opts.AxisOpts(name='城市')) #建立x轴图标
    chart.set_global_opts(yaxis_opts=opts.AxisOpts(name='温度'))
    chart.render('E:/桌面/天气.html')



if __name__ == '__main__':
    main()

4.正则表达式

基本知识

匹配单个字符.jpg
匹配多个字符.jpg

正则表达式常用小案例

import re
#1.匹配电话号码
text = '13691612426'
ret = re.match('1[34578]\d{9}',text)
print(ret.group())
#2.匹配邮箱
text = '1871759153@qq.com'
ret = re.match('\w+@[a-z0-9]+\.[a-z]+',text)
print(ret.group())
#3.匹配url
text = 'https://www.runoob.com/python3/python3-tutorial.html'
ret = re.match('(http|https|ftp)://[^\s]+',text)
print(ret.group())
#4.验证身份证
text = '32042519121281241x'
ret = re.match('\d{17}[\dxX]',text)
print(ret.group())
#5.匹配100内的数字
text = '98'
ret = re.match('[1-9]\d?$|100$',text)
print(ret.group())

group()分组

import re
#group分组
text = 'apple prince is $5,iphone price is $300'
ret = re.match('.*(\$\d+).*(\$\d+)',text)
print(ret.group(1))
print(ret.group(2))

re模块常用函数

import re
# re常用函数
# 1.findall() 找出所有满足条件的，返回的是一个列表
text = 'apple prince is $5,iphone price is $300'
ret = re.findall('\d+',text)
print(ret)
# 2.sub() 找出所有满足条件的并将其替换
text = 'apple prince is $5,iphone price is $300'
ret = re.sub('\d+','0',text)
print(ret)
# 3.split()函数，返回一个列表
text = 'hello world ni hao'
ret = re.split(' ',text)
print(ret)
# 4.compile() 对经常要用的正则表达式进行编译能提高效率
text = 'the number is 20.50'
r = re.compile(r"""
                \d+   #小数点前面的
                \.?   #小数点
                \d+   #小数点后面的
                """,re.VERBOSE)
ret = re.search(r,text)
print(ret.group())

实例分析

#古诗词网爬取（正则表达式的应用）
import requests
import re

poems = []
def page_parse(url):
    headers = {
        "user-agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36"
    }
    resp = requests.get(url,headers=headers)
    text = resp.text
    titles = re.findall(r'<div class="cont">.*?<b>(.*?)</b>',text,re.DOTALL) #加入re.DOTALL使.*可以识别\n
    dynasties = re.findall(r'<p class="source">.*?<a.*?>(.*?)</a>',text,re.DOTALL)
    authors = re.findall(r'<p class="source">.*?<a.*?>.*?<a.*?>(.*?)</a>',text,re.DOTALL)
    contents_tags = re.findall(r'<div class="contson".*?>(.*?)</div>',text,re.DOTALL)
    contents = []
    for content in contents_tags:
        content = re.sub('<.*?>','',content)
        contents.append(content.strip())
    #zip()函数简介
    #zip函数将两个或多个序列作为参数，返回一个组成元素为元组的列表，元组由各序列构成
    # x= [1,2,3]
    # y= [4,5,6]
    # xy = zip(x,y)
    # print(xy)
    #得到[(1,4),(2,5),(3,6)]
    # poems = []
    for x in zip(titles,dynasties,authors,contents):
        title,dynasty,author,content = x
        poem = {
            "title":title,
            "dynasty":dynasty,
            "author":author,
            "content":content
        }
        poems.append(poem)
    # for poem in poems:
    #     print(poem)



def main1():
   base_url = 'https://www.gushiwen.cn/default_{}.aspx'
   for x in range(1,4):
       url = base_url.format(x) #确定前几页url
       page_parse(url)

if __name__ == '__main__':
    main1()
    with open('E:/桌面/poems.txt','w')as fp:
        for poem in poems:
            fp.write("\n"+str(poem))