Python爬虫scrapy框架爬取动态网站——scrapy与selenium结合爬取数据

版权声明：请大家使用时记得显示原创的博主哦！！ https://blog.csdn.net/qq_33472765/article/details/81008120  scrapy框架只能爬取静态网站。如需爬取动态网站，需要结合着selenium进行js的渲染，才能获取到动态加载的数据。

如何通过selenium请求url，而不再通过下载器Downloader去请求这个url?

方法：在request对象通过中间件的时候，在中间件内部开始使用selenium去请求url，并且会得到url对应的源码，然后再将   源 代码通过response对象返回，直接交给process_response()进行处理，再交给引擎。过程中相当于后续中间件的process_request()以及Downloader都跳过了。

相关的配置：

1、scrapy环境中安装selenium：pip install selenium

2、确保python环境中有phantomJS（无头浏览器）

对于selenium的主要操作是下载中间件部分如下图：

代码如下

middlewares.py代码：

注意：自定义下载中间件，采用selenium的方式！！

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

# Define here the models for your spider middleware
#
# See documentation in:
# https://doc.scrapy.org/en/latest/topics/spider-middleware.html

from scrapy import signals
from selenium import webdriver
from selenium.webdriver import FirefoxOptions
from scrapy.http import HtmlResponse, Response
import time

class TaobaospiderSpiderMiddleware(object):
# Not all methods need to be defined. If a method is not defined,
# scrapy acts as if the spider middleware does not modify the
# passed objects.

@classmethod
def from_crawler(cls, crawler):
# This method is used by Scrapy to create your spiders.
s = cls()
crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
return s

def process_spider_input(self, response, spider):
# Called for each response that goes through the spider
# middleware and into the spider.

# Should return None or raise an exception.
return None

def process_spider_output(self, response, result, spider):
# Called with the results returned from the Spider, after
# it has processed the response.

# Must return an iterable of Request, dict or Item objects.
for i in result:
yield i

def process_spider_exception(self, response, exception, spider):
# Called when a spider or process_spider_input() method
# (from other spider middleware) raises an exception.

# Should return either None or an iterable of Response, dict
# or Item objects.
pass

def process_start_requests(self, start_requests, spider):
# Called with the start requests of the spider, and works
# similarly to the process_spider_output() method, except
# that it doesn’t have a response associated.

# Must return only requests (not items).
for r in start_requests:
yield r

def spider_opened(self, spider):
spider.logger.info('Spider opened: %s' % spider.name)

class TaobaospiderDownloaderMiddleware(object):
# Not all methods need to be defined. If a method is not defined,
# scrapy acts as if the downloader middleware does not modify the
# passed objects.

@classmethod
def from_crawler(cls, crawler):
# This method is used by Scrapy to create your spiders.
s = cls()
crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
return s

def process_request(self, request, spider):
# Called for each request that goes through the downloader
# middleware.

# Must either:
# - return None: continue processing this request
# - or return a Response object
# - or return a Request object
# - or raise IgnoreRequest: process_exception() methods of
#   installed downloader middleware will be called
return None

def process_response(self, request, response, spider):
# Called with the response returned from the downloader.

# Must either;
# - return a Response object
# - return a Request object
# - or raise IgnoreRequest
return response

def process_exception(self, request, exception, spider):
# Called when a download handler or a process_request()
# (from other downloader middleware) raises an exception.

# Must either:
# - return None: continue processing this exception
# - return a Response object: stops process_exception() chain
# - return a Request object: stops process_exception() chain
pass

def spider_opened(self, spider):
spider.logger.info('Spider opened: %s' % spider.name)

*********************下面是相应是自定义的下载中间件的替换代码**************************
class SeleniumTaobaoDownloaderMiddleware(object):
# 将driver创建在中间件的初始化方法中，适合项目中只有一个爬虫。
# 爬虫项目中有多个爬虫文件的话，将driver对象的创建放在每一个爬虫文件中。
# def __init__(self):
#     # 在scrapy中创建driver对象，尽可能少的创建该对象。
#     # 1. 在初始化方法中创建driver对象；
#     # 2. 在open_spider中创建deriver对象；
#     # 3. 不要将driver对象的创建放在process_request()；
#     option = FirefoxOptions()
#     option.headless = True
#     self.driver = webdriver.Firefox(options=option)

# 参数spider就是TaobaoSpider()类的对象
def process_request(self, request, spider):
if spider.name == "taobao":
spider.driver.get(request.url)
# 由于淘宝的页面数据加载需要进行滚动，但并不是所有js动态数据都需要滚动。
for x in range(1, 11, 2):
height = float(x) / 10
js = "document.documentElement.scrollTop = document.documentElement.scrollHeight * %f" % height
spider.driver.execute_script(js)
time.sleep(0.2)

origin_code = spider.driver.page_source
# 将源代码构造成为一个Response对象，并返回。
res = HtmlResponse(url=request.url, encoding='utf8', body=origin_code, request=request)
# res = Response(url=request.url, body=bytes(origin_code), request=request)
return res
if spider.name == 'bole':
request.cookies = {}
request.headers.setDefault('User-Agent','')
return None

def process_response(self, request, response, spider):
print(response.url, response.status)
return response

taobao.py 代码如下：

# -*- coding: utf-8 -*-
import scrapy
from selenium import webdriver
from selenium.webdriver import FirefoxOptions

class TaobaoSpider(scrapy.Spider):
"""
scrapy框架只能爬取静态网站。如需爬取动态网站，需要结合着selenium进行js的渲染，才能获取到动态加载的数据。

如何通过selenium请求url，而不再通过下载器Downloader去请求这个url?
方法：在request对象通过中间件的时候，在中间件内部开始使用selenium去请求url，并且会得到url对应的源码，然后再将源代码通过response对象返回，直接交给process_response()进行处理，再交给引擎。过程中相当于后续中间件的process_request()以及Downloader都跳过了。

"""
name = 'taobao'
allowed_domains = ['taobao.com']
start_urls = ['https://s.taobao.com/search?q=%E7%AC%94%E8%AE%B0%E6%9C%AC%E7%94%B5%E8%84%91&imgfile=&commend=all&ssid=s5-e&search_type=item&sourceId=tb.index&spm=a21bo.2017.201856-taobao-item.1&ie=utf8&initiative_id=tbindexz_20170306']

def __init__(self):
# 在初始化淘宝对象时，创建driver
super(TaobaoSpider, self).__init__(name='taobao')
option = FirefoxOptions()
option.headless = True
self.driver = webdriver.Firefox(options=option)

def parse(self, response):
"""
提取列表页的商品标题和价格
:param response:
:return:
"""
info_divs = response.xpath('//div[@class="info-cont"]')
print(len(info_divs))
for div in info_divs:
title = div.xpath('.//a[@class="product-title"]/@title').extract_first('')
price = div.xpath('.//span[contains(@class, "g_price")]/strong/text()').extract_first('')
print(title, price)

settings.py代码如下图：

关于代码中提到的初始化driver的位置有以下两种情况：

1、只存在一个爬虫文件的话，driver初始化函数可以定义在middlewares.py的自定义中间件中（如上述代码注释初始化部分）也可以在爬虫文件中自定义（如上述代码在爬虫文件中初始化）。

注意：如果只有一个爬虫文件就不需要在自定义的process_requsests中判断是哪一个爬虫项目然后分别请求！

2、如果存在两个或两个以上爬虫项目（如下图项目结构）的时候，需要将driver的初始化函数定义在各自的爬虫项目文件下（如上述代码），同时需要在process_requsests判断是那个爬虫项目的请求！！

          

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