Scrapy 的安装

pip3 install Scrapy (mac版)

制作Scrapy 爬虫一共分4步

1. 新建项目
2. 明确目标： 明确你想要爬取的目标
3. 制作爬虫：制作爬虫开始爬取网页
4. 存储内容：设计管道存储爬取内容

命令详解

安装后，在终端直接输入 scrapy，会提示版本及一些命令提示：
scrapy bench : 测试你电脑的scrapy 性能
scrapy fetch + 网址 : 给个URL地址取下载网页信息
scrapy genspider scrapy runspider ： 创建／启动一个爬虫
scrapy shell : 查看环境的
vi settings.py 打开该文档

步骤详解

新建项目
scrapy startproject + 项目名就会自动生成很多文件。

# -*- coding: utf-8 -*-

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

import scrapy

class ItcastItem(scrapy.Item):   # 调用存取字段
    # define the fields for your item here like:
    # name = scrapy.Field()
    # 老师姓名
    name = scrapy.Field()
    # 老师职称
    title = scrapy.Field()
    # 老师信息
    info = scrapy.Field()

settings.py

# -*- coding: utf-8 -*-

# Scrapy settings for ITcast project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     http://doc.scrapy.org/en/latest/topics/settings.html
#     http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
#     http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'ITcast'

SPIDER_MODULES = ['ITcast.spiders']     # 默认帮我们配置好的爬虫位置
NEWSPIDER_MODULE = 'ITcast.spiders'

# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'ITcast (+http://www.yourdomain.com)'

# Obey robots.txt rules   # 表示你的网站是否遵循 robots 协议
ROBOTSTXT_OBEY = True

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32    # 默认请求并发量

# Configure a delay for requests for the same website (default: 0)
# See http://scrapy.readthedocs.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#DOWNLOAD_DELAY = 3     # 下载延迟
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16    # 默认并发请求域的个数
#CONCURRENT_REQUESTS_PER_IP = 16   # 并发请求ip个数

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

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

# Override the default request headers:       # 默认的请求header
#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 http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {        # 爬虫中间键
#    'ITcast.middlewares.ItcastSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {     # 下载中间键，字典格式
#    'ITcast.middlewares.MyCustomDownloaderMiddleware': 543,
#}

# Enable or disable extensions
# See http://scrapy.readthedocs.org/en/latest/topics/extensions.html
#EXTENSIONS = {   # 监控配置
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
#ITEM_PIPELINES = {    # 管道配置文件
#    'ITcast.pipelines.ItcastPipeline': 300,
#}

# Enable and configure the AutoThrottle extension (disabled by default)
# See http://doc.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 http://scrapy.readthedocs.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'

itcast.py

# -*- coding: utf-8 -*-
import scrapy
from ITcast.ITcast.items import ItcastItem

class ItcastSpider(scrapy.Spider):
    name = 'itcast'   # 爬虫名称,启动爬虫时必须执行的参数
    allowed_domains = ['itcast.cn']    # 爬虫允许的域，即遇到其他网址不会爬取,是可选项
    start_urls = ['http://www.itcast.cn/channel/teacher.shtml']   # 表示开始爬时，在这域里获取信息,可以是可迭代对象

    def parse(self, response):    # 解析的方法，每个url完成下载后将被调用
        node_list = response.xpath("//div[@class='li_txt']")
        items = []
        for node in node_list:

            item = ItcastItem()
            # .extract()将xpath转换成 Unicode字符串  xpath返回的一定是列表
            name = node.xpath("./h3/text()").extract()
            title = node.xpath("./h4/text()").extract()
            info = node.xpath("./p/text()").extract()

            item['name'] = name[0]
            item['title'] = title[0]
            item['info'] = info[0]
            items.append(item)
        return items