scrapy入门（深入）-EW帮帮网

Scrapy框架简介

Scrapy是:由Python语言开发的一个快速、高层次的屏幕抓取和web抓取框架，用于抓取web站点并从页面中提取结构化的数据，只需要实现少量的代码，就能够快速的抓取。

新建项目 (scrapy startproject xxx)：新建一个新的爬虫项目
明确目标（编写items.py）：明确你想要抓取的目标
制作爬虫（spiders/xxspider.py）：制作爬虫开始爬取网页
存储内容（pipelines.py）：设计管道存储爬取内容

注意！只有当调度器中不存在任何request了，整个程序才会停止，（也就是说，对于下载失败的URL，Scrapy也会重新下载。）

本篇文章不会讲基本项目创建，创建的话可以移步这个文章，基础的肯定没什么重要性，这篇说明一下一些比较细的知识

Scrapy 官网：https://scrapy.org/
Scrapy 文档：https://docs.scrapy.org/en/latest/
GitHub：https://github.com/scrapy/scrapy/

基本结构

定义爬取的数据结构

首先在items中定义一个需要爬取的数据结构
```
class ScrapySpiderItem(scrapy.Item):
    # 创建一个类来定义爬取的数据结构
    name = scrapy.Field()
    title = scrapy.Field()
    url = scrapy.Field()
```
那为什么要这样定义：

在Scrapy框架中，scrapy.Field() 是用于定义Item字段的特殊类，它的作用相当于一个标记。具体来说：
1. 数据结构声明
  每个Field实例代表Item中的一个数据字段（如你代码中的name/title/url），用于声明爬虫要收集哪些数据字段。
2. 元数据容器
  虽然看起来像普通赋值，但实际可以通过Field()传递元数据参数：
在这里定义变量之后，后续就可以这样进行使用
```
item = ScrapySpiderItem()
item['name'] = '股票名称'
item['title'] = '股价数据'
item['url'] = 'http://example.com'
```
然后就可以输入scrapy genspider itcast "itcast.cn"命令来创建一个爬虫，爬取itcast.cn域里的代码

数据爬取

注意这里如果你是跟着菜鸟教程来的，一定要改为这样，在itcast.py中

import scrapy


class ItcastSpider(scrapy.Spider):
    name = "itcast"
    allowed_domains = ["iscast.cn"]
    start_urls = ["http://www.itcast.cn/channel/teacher.shtml"]

    def parse(self, response):
        filename = "teacher.html"
        open(filename, 'wb').write(response.body)

改为wb，因为返回的是byte数据，如果用w不能正常返回值

那么基本的框架就是这样：

from mySpider.items import ItcastItem

def parse(self, response):
    #open("teacher.html","wb").write(response.body).close()

    # 存放老师信息的集合
    items = []

    for each in response.xpath("//div[@class='li_txt']"):
        # 将我们得到的数据封装到一个 `ItcastItem` 对象
        item = ItcastItem()
        #extract()方法返回的都是unicode字符串
        name = each.xpath("h3/text()").extract()
        title = each.xpath("h4/text()").extract()
        info = each.xpath("p/text()").extract()

        #xpath返回的是包含一个元素的列表
        item['name'] = name[0]
        item['title'] = title[0]
        item['info'] = info[0]

        items.append(item)

    # 直接返回最后数据
    return items

爬取信息后，使用xpath提取信息，返回值转化为unicode编码后储存到声明好的变量中，返回

数据保存

主要有四种格式

scrapy crawl itcast -o teachers.json

scrapy crawl itcast -o teachers.jsonl //json lines格式

scrapy crawl itcast -o teachers.csv

scrapy crawl itcast -o teachers.xml

不过上面只是一些项目的搭建和基本使用，我们通过爬虫渐渐进入框架，一定也好奇这个框架的优点在哪里，有什么特别的作用

scrapy结构

pipelines（管道）

这个文件也就是我们说的管道,当Item在Spider中被收集之后，它将会被传递到Item Pipeline(管道)，这些Item Pipeline组件按定义的顺序处理Item。每个Item Pipeline都是实现了简单方法的Python类，比如决定此Item是丢弃而存储。以下是item pipeline的一些典型应用：

验证爬取的数据(检查item包含某些字段，比如说name字段)
查重(并丢弃)
将爬取结果保存到文件或者数据库中

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://docs.scrapy.org/en/latest/topics/item-pipeline.html


# useful for handling different item types with a single interface
from itemadapter import ItemAdapter


class MyspiderPipeline:
    def process_item(self, item, spider):
        return item

settings（设置）

代码里给了注释，一些基本的设置

# Scrapy settings for mySpider project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#项目名称
BOT_NAME = "mySpider"

SPIDER_MODULES = ["mySpider.spiders"]
NEWSPIDER_MODULE = "mySpider.spiders"


# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = "mySpider (+http://www.yourdomain.com)"
#是否遵守规则协议
# Obey robots.txt rules
ROBOTSTXT_OBEY = True

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32 #最大并发量32，默认16

# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#下载延迟3秒
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#请求头
#DEFAULT_REQUEST_HEADERS = {
#    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
#    "Accept-Language": "en",
#}

# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    "mySpider.middlewares.MyspiderSpiderMiddleware": 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    "mySpider.middlewares.MyspiderDownloaderMiddleware": 543,
#}

# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    "scrapy.extensions.telnet.TelnetConsole": None,
#}

# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
#ITEM_PIPELINES = {
#    "mySpider.pipelines.MyspiderPipeline": 300,
#}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = "httpcache"
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = "scrapy.extensions.httpcache.FilesystemCacheStorage"

# Set settings whose default value is deprecated to a future-proof value
TWISTED_REACTOR = "twisted.internet.asyncioreactor.AsyncioSelectorReactor"
FEED_EXPORT_ENCODING = "utf-8"

spiders

爬虫代码目录，定义了爬虫的逻辑

import scrapy
from mySpider.items import ItcastItem

class ItcastSpider(scrapy.Spider):
    name = "itcast"
    allowed_domains = ["iscast.cn"]
    start_urls = ["http://www.itcast.cn/"]

    def parse(self, response):
        # 获取网站标题
        list=response.xpath('//*[@id="mCSB_1_container"]/ul/li[@*]')

实战（大学信息）

目标网站：爬取大学信息

base64：

aHR0cDovL3NoYW5naGFpcmFua2luZy5jbi9yYW5raW5ncy9iY3VyLzIwMjQ=

变量命名

在刚刚创建的itcast里更改一下域名，在items里改一下接收数据格式

itcast.py

import scrapy
from mySpider.items import ItcastItem

class ItcastSpider(scrapy.Spider):
    name = "itcast"
    allowed_domains = ["iscast.cn"]
    start_urls = ["https://www.shanghairanking.cn/rankings/bcur/2024"]

    def parse(self, response):
        # 获取网站标题
        list=response.xpath('(//*[@class="align-left"])[position() > 1 and position() <= 31]')
        item=ItcastItem()
        for i in list:
            name=i.xpath('./div/div[2]/div[1]/div/div/span/text()').extract()
            description=i.xpath('./div/div[2]/p/text()').extract()
            location=i.xpath('../td[3]/text()').extract()
            item['name']=str(name).strip().replace('\\n','').replace(' ','')
            item['description']=str(description).strip().replace('\\n','').replace(' ','')
            item['location']=str(location).strip().replace('\\n','').replace(' ','')
            print(item)
            yield item

这里xpath感不太了解的可以看我之前的博客

一些爬虫基础知识备忘录-xpath

items.py

# Define here the models for your scraped items
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/items.html

import scrapy

class ItcastItem(scrapy.Item):
   name = scrapy.Field()
   description=scrapy.Field()
   location=scrapy.Field()

pipelines.py

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://docs.scrapy.org/en/latest/topics/item-pipeline.html


# useful for handling different item types with a single interface
import csv
from itemadapter import ItemAdapter


class MyspiderPipeline:
    def __init__(self):#在初始化函数中先创建一个csv文件
        self.f=open('school.csv','w',encoding='utf-8',newline='')
        self.file_name=['name','description','location']
        self.writer=csv.DictWriter(self.f,fieldnames=self.file_name)
        self.writer.writeheader()#写入第一段字段名
    def process_item(self, item, spider):
        self.writer.writerow(dict(item))#在写入的时候，要转化为字典对象
        print(item)
        return item
    def close_spider(self,spider):
        self.f.close()#关闭文件

setting.py

# Scrapy settings for mySpider project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#项目名称
BOT_NAME = "mySpider"

SPIDER_MODULES = ["mySpider.spiders"]
NEWSPIDER_MODULE = "mySpider.spiders"


# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = "mySpider (+http://www.yourdomain.com)"
#是否遵守规则协议
# Obey robots.txt rules
ROBOTSTXT_OBEY = False

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32 #最大并发量32，默认16

# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#下载延迟3秒
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#请求头
DEFAULT_REQUEST_HEADERS = {
   "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
   "Accept-Language": "en",
}

# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    "mySpider.middlewares.MyspiderSpiderMiddleware": 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    "mySpider.middlewares.MyspiderDownloaderMiddleware": 543,
#}

# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    "scrapy.extensions.telnet.TelnetConsole": None,
#}

# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
   "mySpider.pipelines.MyspiderPipeline": 300,
}
LOG_LEVEL = 'WARNING'
# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = "httpcache"
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = "scrapy.extensions.httpcache.FilesystemCacheStorage"

# Set settings whose default value is deprecated to a future-proof value
TWISTED_REACTOR = "twisted.internet.asyncioreactor.AsyncioSelectorReactor"
FEED_EXPORT_ENCODING = "utf-8"

start.py

然后在myspider文件夹下可以创建一个start.py文件，这样我们直接运行这个文件即可，不需要使用命令

from scrapy import cmdline
cmdline.execute("scrapy crawl itcast".split())

然后我们就正常保存为csv格式啦！

一些问题

实现继续爬取，翻页

scrapy使用yield进行数据解析和爬取request，如果想实现翻页或者在请求完单次请求后继续请求，使用yield继续请求如果这里你使用一个return肯定会直接退出，感兴趣的可以去深入了解一下

一些setting配置

LOG_LEVEL = 'WARNING'可以把不太重要的日志关掉，让我们专注于看数据的爬取与分析

然后管道什么的在运行前记得开一下,把原先注释掉的打开就行

另外robot也要记得关一下

然后管道什么的在运行前记得开一下

文件命名

csv格式的文件命名一定要和items中的命名一致，不然数据进不去

到了结束的时候了，本篇文章是对scrapy框架的入门，更加深入的知识请期待后续文章，一起进步！

scrapy入门（深入）