爬虫scrapy框架及案例：入门及使用

P3 03sacrapy的入门使用

安装 scrapy

# 复用pip安装scrapy
pip3 install scrapy

# 升级(将pip3变成pip默认)
/usr/local/opt/python@3.9/bin/python3.9 -m pip install --upgrade pip

查看安装情况

scrapy-notes/src/2022 on 🌱 master 
❯ scrapy --version
Scrapy 2.5.1 - no active project

Usage:
  scrapy <command> [options] [args]

Available commands:
  bench         Run quick benchmark test
  commands      
  fetch         Fetch a URL using the Scrapy downloader
  genspider     Generate new spider using pre-defined templates
  runspider     Run a self-contained spider (without creating a project)
  settings      Get settings values
  shell         Interactive scraping console
  startproject  Create new project
  version       Print Scrapy version
  view          Open URL in browser, as seen by Scrapy

  [ more ]      More commands available when run from project directory

Use "scrapy <command> -h" to see more info about a command

常用的命令

# 创建一个项目(myspider 是项目名)
scrapy startproject myspider
# 生成一个爬虫`itcast`，指定范围(itcast.cn，一般写域名)
cd myspider
scrapy genspider itcast itcast.cn
# 启动一个爬虫(带参数爬虫名: itcast)
scrapy crawl itcast

项目结构

.
└── myspider
    ├── myspider
    │   ├── __init__.py
    │   ├── items.py
    │   ├── middlewares.py
    │   ├── pipelines.py
    │   ├── settings.py
    │   └── spiders
    │       └── __init__.py
    └── scrapy.cfg

pipline的设置

# 定义 pipline 以及 优先级，越小，越先被执行
#ITEM_PIPELINES = {
#    'myspider.pipelines.MyspiderPipeline': 300,
#}

# 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

总结，爬虫几步曲

1. 创建一个爬虫项目 startproject
2. 生成爬虫，可能是1个，可能是多个  genspider
3. 提取数据 ，使用 xpath/css 等方法
4. 保存数据 ，复用 pipline