第十单元：Scrapy爬虫框架

框架介绍

入口：SPIDERS(提供要访问的url连接，提取访问内容）
出口：ITEM PIPLINES（提取后处理）

框架解析

requests库和scrapy库的比较

scrapy爬虫的常用命令

第十一单元：Scrapy爬虫基本使用

第一个实例

创建一个爬虫

然后需要配置demo.py文件
parse函数就是爬取函数，需要我们写具体功能
从网页爬取内容对应的对象response存储在文件中

import scrapy

class DemoSpider(scrapy.Spider):
    name = 'demo'
    #allowed_domains = ['demo.io']
    start_urls = ['https://python123.io/ws/demo.html']

    def parse(self, response):
        fname = response.url.split('/')[-1]
        with open(fname,'wb') as f:
            f.write(response.body)
        self.log('Saved file %s.' % name)

然后执行scrapy crawl demo
即可在目录下获得抓取的网站页面

yield关键字的使用

在gen函数的for循环中，每次调用生成器会返回一个值


使用for循环每次提交urls列表中的一个url请求，这是一种生成器写法，每次返回一个url连接

Scrapy爬虫的基本使用

Request类

Response类

Item类

键值对封装

第十二单元：实例：股票数据Scrapy爬虫（见PPT，现不可用）

下面是stocks.py文件源代码

# -*- coding: utf-8 -*-
import scrapy
import re


class StocksSpider(scrapy.Spider):
    name = "stocks"
    start_urls = ['https://quote.eastmoney.com/stocklist.html']

    def parse(self, response):
        for href in response.css('a::attr(href)').extract():
            try:
                stock = re.findall(r"[s][hz]\d{6}", href)[0]
                url = 'https://gupiao.baidu.com/stock/' + stock + '.html'
                yield scrapy.Request(url, callback=self.parse_stock)
            except:
                continue

    def parse_stock(self, response):
        infoDict = {}
        stockInfo = response.css('.stock-bets')
        name = stockInfo.css('.bets-name').extract()[0]
        keyList = stockInfo.css('dt').extract()
        valueList = stockInfo.css('dd').extract()
        for i in range(len(keyList)):
            key = re.findall(r'>.*</dt>', keyList[i])[0][1:-5]
            try:
                val = re.findall(r'\d+\.?.*</dd>', valueList[i])[0][0:-5]
            except:
                val = '--'
            infoDict[key]=val

        infoDict.update(
            {'股票名称': re.findall('\s.*\(',name)[0].split()[0] + \
             re.findall('\>.*\<', name)[0][1:-1]})
        yield infoDict

下面是pipelines.py文件源代码：

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

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


class BaidustocksPipeline(object):
    def process_item(self, item, spider):
        return item

class BaidustocksInfoPipeline(object):
    def open_spider(self, spider):
        self.f = open('BaiduStockInfo.txt', 'w')

    def close_spider(self, spider):
        self.f.close()

    def process_item(self, item, spider):
        try:
            line = str(dict(item)) + '\n'
            self.f.write(line)
        except:
            pass
        return item

下面是settings.py文件中被修改的区域：

# Configure item pipelines
# See https://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
    'BaiduStocks.pipelines.BaidustocksInfoPipeline': 300,
}

完结散花~