怎么在每次执行python之前都执行固定的代码 python每次运行前会保存吗

1.下载包

pip install scrapy

2.在使用路径终端上创建项目指令： scrapy startproject 项目名

爬虫文件名和爬虫名称不能相同，spiders目录内不能存在相同的爬虫名称的项目文件

scrapy startproject maoyan

cd maoyan

scrapy genspider maoyan https://www.maoyan.com/

创建后目录大致页如下

|-ProjectName #项目文件夹

|-ProjectName #项目目录

|-items.py #定义数据结构

|-middlewares.py #中间件

|-pipelines.py #数据处理

|-settings.py #全局配置

|-spiders

|-__init__.py #爬虫文件

|-maoyan.py

|-scrapy.cfg #项目基本配置文件

3.settings设置如下： 

# 项目名
BOT_NAME = 'maoyan'

SPIDER_MODULES = ['maoyan.spiders']
NEWSPIDER_MODULE = 'maoyan.spiders'

USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36'

# ROBOTSTXT_OBEY：是否遵循机器人协议，默认是true，需要改为false
ROBOTSTXT_OBEY = False

# CONCURRENT_REQUESTS：最大并发数，同时允许开启多少个爬虫线程
#CONCURRENT_REQUESTS = 32

# 下载延迟时间，单位是秒，控制爬虫爬取的频率
DOWNLOAD_DELAY = 3

# DEFAULT_REQUEST_HEADERS：默认请求头，上面写了一个USER_AGENT，这个东西就是放在请求头里面的，可以根据你爬取的内容做相应设置。
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

#ITEM_PIPELINES：项目管道，300为优先级，越低越爬取的优先度越高
ITEM_PIPELINES = {
   'myfirstPj.pipelines.MyfirstpjPipeline': 300,
}
#比如pipelines.py里面写了两个管道，一个爬取网页的管道，一个存数据库的管道，调整他们的优先级，如果有爬虫数据，优先执行存库操作。

#编码格式 , 不设置的话json就会乱码

FEED_EXPORT_ENCODING = 'utf-8'

USER_AGENT 在浏览器中可看到：

 4.在items.py上编写需要抓取的内容

 

import scrapy

class MaoyanItem(scrapy.Item):
    move_name=scrapy.Field()
    peaple_name=scrapy.Field()
    move_time = scrapy.Field()
    describe= scrapy.Field()

 5.创建一个maoyan_spider.py文件

 

 

 6.在 maoyan_spider.py上编写 

 

 

 

 将复制出来的一大行的（包括电影名人名时间的）xpath先写起来，再复制下一行的xpath，再写起来，对比就可以发现规律了，通过循环每一大行，再细定位就可以了，细定位同样的单独复制两个电影名就可以发现其中的区别了

这是一大行的定位： //*[@id="app"]/div/div/div[1]/dl/dd[1]/div/div/div[1]，//*[@id="app"]/div/div/div[1]/dl/dd[2]/div/div/div[1]可以看出dd[]是变量，所以在它前面的都是固定的，用//替换dd[]，就可以得到一整页的行了，move_list=//*[@id='app']/div/div/div[1]/dl//div/div/div[1]

电影名为//*[@id="app"]/div/div/div[1]/dl/dd[3]/div/div/div[1]/p[1]/a ，时间为：//*[@id="app"]/div/div/div[1]/dl/dd[3]/div/div/div[1]/p[3]，可以看出在for循环每一行里面共用的开头那部分就是刚刚定位的一大行move_list的可以用" . "表示，".//p[1]/a"，".//p[3]"

当然你也可以直接看网页中的标签自己写出来，方法不唯一

aaa=d.xpath(".//p[1]/a").extract_first() # 这是输出的第一个数据

输出之后接下来就是字符串的处理了。

这里没有下一页的功能，这里没有下一页的功能，大部分网页翻页功能一般方法：看网址是否有变量比如10,20，或者点击下一页按钮，同样也可以看request请求的变量。

 

import scrapy
from maoyan.items import MaoyanItem

class MaoyanSpiderSpider(scrapy.Spider):
    name = 'maoyan_spider' #项目名
    allowed_domains = ['maoyan.com'] #域名
    #url入口
    start_urls = ['https://www.maoyan.com/board/4?timeStamp=1638539026134&channelId=40011&index=1&signKey=a675982b76014e4a8b7f3beb5afe7441&sVersion=1&webdriver=false']

    def parse(self, response):
        # //*[@id="app"]/div/div/div[1]/dl/dd[3]/div
        move_list = response.xpath("//*[@id='app']/div/div/div[1]/dl//div/div/div[1]")
        for d in move_list:
            maoyan_item=MaoyanItem()## 初始化item对象保存爬取的信息
            # //*[@id="app"]/div/div/div[1]/dl/dd[3]/div/div/div[1]/p[1]/a ----------name
            # //*[@id="app"]/div/div/div[1]/dl/dd[3]/div/div/div[1]/p[3] ------------time
            # //*[@id="app"]/div/div/div[1]/dl/dd[3]/div/div/div[1]/p[2] ------------peaple
            n_list= []
            p_list= []
            # 电影名
            aaa=d.xpath(".//p[1]/a").extract_first().split('"') # 切割第一个数据
            for aa in aaa:
                n_list.append(aa)
            maoyan_item['move_name'] = n_list[3]
            # 主演
            bbb=d.xpath(".//p[2]").extract_first().split('\n')
            for bb in bbb:
                p_list.append(bb)
            maoyan_item['peaple_name'] = p_list[1].replace('主演：','').strip()
            # 上映时间
            move_time1 = d.xpath(".//p[3]").extract()
            for t in move_time1:
                ccc=re.search(r"(\d{4}-\d{1,2}-\d{1,2})",t).group(0)
                maoyan_item['move_time'] =ccc
            print(maoyan_item)
            yield maoyan_item   # 提交到调度器

7.手动创建一个main.py,用来运行的，也可以用指令

from scrapy import cmdline
cmdline.execute('scrapy crawl maoyan_spider'.split())

8.运行main.py 

9.存储方式：json,csv,mysql

 1)保存到json——注意路径

scrapy crawl maoyan_spider -o test.json

 

 2）保存到csv——注意路径

scrapy crawl maoyan_spider -o test.csv

 

3）保存到数据库mysql

数据库自己先建好表和字段，这里是直接插入数据的

#settings.py
# mongo_host='192.168.x.xxx'
# mongo_post=27017
# mongo_db_name='maoyan'
# mongo_db_collection='maoyan_movie'

MYSQL_HOST = 'localhost'
MYSQL_DBNAME = 'maoyan_sql'
MYSQL_USER = 'root'
MYSQL_PASSWD = '1234'

 

#pipelines.py
# mongo_host='192.168.x.xxx'
# mongo_post=27017
# mongo_db_name='maoyan'
# mongo_db_collection='maoyan_movie'
MYSQL_HOST = 'localhost'
MYSQL_DBNAME = 'maoyan_sql'
MYSQL_USER = 'root'
MYSQL_PASSWD = '1234'#pipelines.py
from itemadapter import ItemAdapter
import pymysql
from sqlalchemy import *
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from datetime import datetime
#连接数据库
from maoyan import settings
def dbHandle():
    conn = pymysql.connect(
        host = "localhost",
        user = "root",
        passwd = "1234",
        charset = "utf8mp4",
        use_unicode = False
    )
    return conn
class MaoyanPipeline:
    def __init__(self):
        # 连接数据库
        self.connect = pymysql.connect(
            host=settings.MYSQL_HOST,
            db=settings.MYSQL_DBNAME,
            user=settings.MYSQL_USER,
            passwd=settings.MYSQL_PASSWD,
            charset='utf8',
            use_unicode=True)
        # 通过cursor执行增删查改
        self.cursor = self.connect.cursor()
    def process_item(self, item, spider):
        try:
            # 插入数据
            self.cursor.execute(
                """insert into move(move_name,peaple_name,move_time) value (%s, %s, %s)""",
                (item['move_name'],
                 item['peaple_name'],
                 item['move_time']))
            # 提交sql语句
            self.connect.commit()
        except BaseException as e:
            # 出现错误时打印错误日志
            print("error:------------", e, "-----------------")
        return item
#dbmongo部分参考
    # def __init__(self):
    #     host=mongo_host
    #     post=mongo_post
    #     dbname=mongo_db_name
    #     sheetname=mongo_db_collection
    #     client=pymongo.MongoClient(host=host,post=post)
    #     mydb=client[dbname]
    #     self.post=mydb[sheetname]#读写操作
    # def process_item(self, item, spider):
    #     data=dict(item)#先转字典，再数据插入
    #     self.post.insert(data)
    #     return item
# # class HellospiderPipeline(object):
#     def process_item(self, item, spider):
#         dbObject = dbHandle()
#         cursor = dbObject.cursor()
#         cursor.execute("USE maoyan_sql")
#         #插入数据库
#         sql = "INSERT INTO move(move_name,peaple_name,move_time) VALUES(%s,%s,%s)"
#         try:
#             cursor.execute(sql,
#                            ( item['move_name'], item['peaple_name'], item['move_time']))
#             cursor.connection.commit()
#         except BaseException as e:
#             print("错误在这里>>>>>>>>>>>>>", e, "<<<<<<<<<<<<<")
#             dbObject.rollback()
#         return item

 

 

 

数据库中查看如下：

 

结尾：#以下仅供参考：

#middlewares.py
#定义ip代理中间件
import base64
class my_proxy(object):
    def process_request(self,request,spider):
        request.meta['proxy']='http-xxx.com:端口号'
        proxy_name_pass=b'用户名：密码'
        encode_pass_name=base64.b64encode(proxy_name_pass)#加密
        request.headers['proxy-Authorization']='Basic '+encode_pass_name.decode()

#中间件定义之后一定要在settings文件内启用

#settings.py
DOWNLOADER_MIDDLEWARES = {
   # 'maoyan.middlewares.MaoyanDownloaderMiddleware': 543,
   'maoyan.middlewares.my_proxy': 543
}


#middlewares.py
#定义useragent中间件
class my_useragent(object):
    def process_request(self,request,spider):
        USER_AGENT_LIST=[百度一下就有]
        agent=random.choice(USER_AGENT_LIST)
        request.headers['User_Agent']=agent

#settings.py优先级不能相同
DOWNLOADER_MIDDLEWARES = {
   'maoyan.middlewares.my_proxy': 543,
   'maoyan.middlewares.my_uesragent': 544,
}