高性能相关、Scrapy框架

2019年11月18日 阅读数:102
这篇文章主要向大家介绍高性能相关、Scrapy框架,主要内容包括基础应用、实用技巧、原理机制等方面,希望对大家有所帮助。

高性能相关

在编写爬虫时,性能的消耗主要在IO请求中,当单进程单线程模式下请求URL时必然会引发等待,从而使得请求总体变慢。html

 1 import requests
 2 
 3 def fetch_async(url):
 4     response = requests.get(url)
 5     return response
 6 
 7 
 8 url_list = ['http://www.github.com', 'http://www.bing.com']
 9 
10 for url in url_list:
11     fetch_async(url)
1.同步执行
 1 from concurrent.futures import ThreadPoolExecutor
 2 import requests
 3 
 4 
 5 def fetch_async(url):
 6     response = requests.get(url)
 7     return response
 8 
 9 
10 url_list = ['http://www.github.com', 'http://www.bing.com']
11 pool = ThreadPoolExecutor(5)
12 for url in url_list:
13     pool.submit(fetch_async, url)
14 pool.shutdown(wait=True)
2.多线程执行
 1 from concurrent.futures import ThreadPoolExecutor
 2 import requests
 3 
 4 def fetch_async(url):
 5     response = requests.get(url)
 6     return response
 7 
 8 
 9 def callback(future):
10     print(future.result())
11 
12 
13 url_list = ['http://www.github.com', 'http://www.bing.com']
14 pool = ThreadPoolExecutor(5)
15 for url in url_list:
16     v = pool.submit(fetch_async, url)
17     v.add_done_callback(callback)
18 pool.shutdown(wait=True)
2.多线程+回调函数执行
 1 from concurrent.futures import ProcessPoolExecutor
 2 import requests
 3 
 4 def fetch_async(url):
 5     response = requests.get(url)
 6     return response
 7 
 8 
 9 url_list = ['http://www.github.com', 'http://www.bing.com']
10 pool = ProcessPoolExecutor(5)
11 for url in url_list:
12     pool.submit(fetch_async, url)
13 pool.shutdown(wait=True)
3.多进程执行
 1 from concurrent.futures import ProcessPoolExecutor
 2 import requests
 3 
 4 
 5 def fetch_async(url):
 6     response = requests.get(url)
 7     return response
 8 
 9 
10 def callback(future):
11     print(future.result())
12 
13 
14 url_list = ['http://www.github.com', 'http://www.bing.com']
15 pool = ProcessPoolExecutor(5)
16 for url in url_list:
17     v = pool.submit(fetch_async, url)
18     v.add_done_callback(callback)
19 pool.shutdown(wait=True)
3.多进程+回调函数执行

经过上述代码都可以完成对请求性能的提升,对于多线程和多进行的缺点是在IO阻塞时会形成了线程和进程的浪费,因此异步IO回事首选:python

 1 import asyncio
 2 
 3 
 4 @asyncio.coroutine
 5 def func1():
 6     print('before...func1......')
 7     yield from asyncio.sleep(5)
 8     print('end...func1......')
 9 
10 
11 tasks = [func1(), func1()]
12 
13 loop = asyncio.get_event_loop()
14 loop.run_until_complete(asyncio.gather(*tasks))
15 loop.close()
1.asyncio示例1
 1 import asyncio
 2 
 3 
 4 @asyncio.coroutine
 5 def fetch_async(host, url='/'):
 6     print(host, url)
 7     reader, writer = yield from asyncio.open_connection(host, 80)
 8 
 9     request_header_content = """GET %s HTTP/1.0\r\nHost: %s\r\n\r\n""" % (url, host,)
10     request_header_content = bytes(request_header_content, encoding='utf-8')
11 
12     writer.write(request_header_content)
13     yield from writer.drain()
14     text = yield from reader.read()
15     print(host, url, text)
16     writer.close()
17 
18 tasks = [
19     fetch_async('www.cnblogs.com', '/wupeiqi/'),
20     fetch_async('dig.chouti.com', '/pic/show?nid=4073644713430508&lid=10273091')
21 ]
22 
23 loop = asyncio.get_event_loop()
24 results = loop.run_until_complete(asyncio.gather(*tasks))
25 loop.close()
1.asyncio示例2
 1 import aiohttp
 2 import asyncio
 3 
 4 
 5 @asyncio.coroutine
 6 def fetch_async(url):
 7     print(url)
 8     response = yield from aiohttp.request('GET', url)
 9     # data = yield from response.read()
10     # print(url, data)
11     print(url, response)
12     response.close()
13 
14 
15 tasks = [fetch_async('http://www.google.com/'), fetch_async('http://www.chouti.com/')]
16 
17 event_loop = asyncio.get_event_loop()
18 results = event_loop.run_until_complete(asyncio.gather(*tasks))
19 event_loop.close()
2.asyncio + aiohttp
 1 import asyncio
 2 import requests
 3 
 4 
 5 @asyncio.coroutine
 6 def fetch_async(func, *args):
 7     loop = asyncio.get_event_loop()
 8     future = loop.run_in_executor(None, func, *args)
 9     response = yield from future
10     print(response.url, response.content)
11 
12 
13 tasks = [
14     fetch_async(requests.get, 'http://www.cnblogs.com/wupeiqi/'),
15     fetch_async(requests.get, 'http://dig.chouti.com/pic/show?nid=4073644713430508&lid=10273091')
16 ]
17 
18 loop = asyncio.get_event_loop()
19 results = loop.run_until_complete(asyncio.gather(*tasks))
20 loop.close()
3.asyncio + requests
 1 import gevent
 2 
 3 import requests
 4 from gevent import monkey
 5 
 6 monkey.patch_all()
 7 
 8 
 9 def fetch_async(method, url, req_kwargs):
10     print(method, url, req_kwargs)
11     response = requests.request(method=method, url=url, **req_kwargs)
12     print(response.url, response.content)
13 
14 # ##### 发送请求 #####
15 gevent.joinall([
16     gevent.spawn(fetch_async, method='get', url='https://www.python.org/', req_kwargs={}),
17     gevent.spawn(fetch_async, method='get', url='https://www.yahoo.com/', req_kwargs={}),
18     gevent.spawn(fetch_async, method='get', url='https://github.com/', req_kwargs={}),
19 ])
20 
21 # ##### 发送请求(协程池控制最大协程数量) #####
22 # from gevent.pool import Pool
23 # pool = Pool(None)
24 # gevent.joinall([
25 #     pool.spawn(fetch_async, method='get', url='https://www.python.org/', req_kwargs={}),
26 #     pool.spawn(fetch_async, method='get', url='https://www.yahoo.com/', req_kwargs={}),
27 #     pool.spawn(fetch_async, method='get', url='https://www.github.com/', req_kwargs={}),
28 # ])
4.gevent + requests
 1 import grequests
 2 
 3 
 4 request_list = [
 5     grequests.get('http://httpbin.org/delay/1', timeout=0.001),
 6     grequests.get('http://fakedomain/'),
 7     grequests.get('http://httpbin.org/status/500')
 8 ]
 9 
10 
11 # ##### 执行并获取响应列表 #####
12 # response_list = grequests.map(request_list)
13 # print(response_list)
14 
15 
16 # ##### 执行并获取响应列表(处理异常) #####
17 # def exception_handler(request, exception):
18 # print(request,exception)
19 #     print("Request failed")
20 
21 # response_list = grequests.map(request_list, exception_handler=exception_handler)
22 # print(response_list)
5.grequests
 1 from twisted.web.client import getPage, defer
 2 from twisted.internet import reactor
 3 
 4 
 5 def all_done(arg):
 6     reactor.stop()
 7 
 8 
 9 def callback(contents):
10     print(contents)
11 
12 
13 deferred_list = []
14 
15 url_list = ['http://www.bing.com', 'http://www.baidu.com', ]
16 for url in url_list:
17     deferred = getPage(bytes(url, encoding='utf8'))
18     deferred.addCallback(callback)
19     deferred_list.append(deferred)
20 
21 dlist = defer.DeferredList(deferred_list)
22 dlist.addBoth(all_done)
23 
24 reactor.run()
6.Twisted示例
 1 from tornado.httpclient import AsyncHTTPClient
 2 from tornado.httpclient import HTTPRequest
 3 from tornado import ioloop
 4 
 5 
 6 def handle_response(response):
 7     """
 8     处理返回值内容(须要维护计数器,来中止IO循环),调用 ioloop.IOLoop.current().stop()
 9     :param response: 
10     :return: 
11     """
12     if response.error:
13         print("Error:", response.error)
14     else:
15         print(response.body)
16 
17 
18 def func():
19     url_list = [
20         'http://www.baidu.com',
21         'http://www.bing.com',
22     ]
23     for url in url_list:
24         print(url)
25         http_client = AsyncHTTPClient()
26         http_client.fetch(HTTPRequest(url), handle_response)
27 
28 
29 ioloop.IOLoop.current().add_callback(func)
30 ioloop.IOLoop.current().start()
7.Tornado
 1 from twisted.internet import reactor
 2 from twisted.web.client import getPage
 3 import urllib.parse
 4 
 5 
 6 def one_done(arg):
 7     print(arg)
 8     reactor.stop()
 9 
10 post_data = urllib.parse.urlencode({'check_data': 'adf'})
11 post_data = bytes(post_data, encoding='utf8')
12 headers = {b'Content-Type': b'application/x-www-form-urlencoded'}
13 response = getPage(bytes('http://dig.chouti.com/login', encoding='utf8'),
14                    method=bytes('POST', encoding='utf8'),
15                    postdata=post_data,
16                    cookies={},
17                    headers=headers)
18 response.addBoth(one_done)
19 
20 reactor.run()
Twisted更多

以上均是Python内置以及第三方模块提供异步IO请求模块,使用简便大大提升效率,而对于异步IO请求的本质则是【非阻塞Socket】+【IO多路复用】:react

  1 import select
  2 import socket
  3 import time
  4 
  5 
  6 class AsyncTimeoutException(TimeoutError):
  7     """
  8     请求超时异常类
  9     """
 10 
 11     def __init__(self, msg):
 12         self.msg = msg
 13         super(AsyncTimeoutException, self).__init__(msg)
 14 
 15 
 16 class HttpContext(object):
 17     """封装请求和相应的基本数据"""
 18 
 19     def __init__(self, sock, host, port, method, url, data, callback, timeout=5):
 20         """
 21         sock: 请求的客户端socket对象
 22         host: 请求的主机名
 23         port: 请求的端口
 24         port: 请求的端口
 25         method: 请求方式
 26         url: 请求的URL
 27         data: 请求时请求体中的数据
 28         callback: 请求完成后的回调函数
 29         timeout: 请求的超时时间
 30         """
 31         self.sock = sock
 32         self.callback = callback
 33         self.host = host
 34         self.port = port
 35         self.method = method
 36         self.url = url
 37         self.data = data
 38 
 39         self.timeout = timeout
 40 
 41         self.__start_time = time.time()
 42         self.__buffer = []
 43 
 44     def is_timeout(self):
 45         """当前请求是否已经超时"""
 46         current_time = time.time()
 47         if (self.__start_time + self.timeout) < current_time:
 48             return True
 49 
 50     def fileno(self):
 51         """请求sockect对象的文件描述符,用于select监听"""
 52         return self.sock.fileno()
 53 
 54     def write(self, data):
 55         """在buffer中写入响应内容"""
 56         self.__buffer.append(data)
 57 
 58     def finish(self, exc=None):
 59         """在buffer中写入响应内容完成,执行请求的回调函数"""
 60         if not exc:
 61             response = b''.join(self.__buffer)
 62             self.callback(self, response, exc)
 63         else:
 64             self.callback(self, None, exc)
 65 
 66     def send_request_data(self):
 67         content = """%s %s HTTP/1.0\r\nHost: %s\r\n\r\n%s""" % (
 68             self.method.upper(), self.url, self.host, self.data,)
 69 
 70         return content.encode(encoding='utf8')
 71 
 72 
 73 class AsyncRequest(object):
 74     def __init__(self):
 75         self.fds = []
 76         self.connections = []
 77 
 78     def add_request(self, host, port, method, url, data, callback, timeout):
 79         """建立一个要请求"""
 80         client = socket.socket()
 81         client.setblocking(False)
 82         try:
 83             client.connect((host, port))
 84         except BlockingIOError as e:
 85             pass
 86             # print('已经向远程发送链接的请求')
 87         req = HttpContext(client, host, port, method, url, data, callback, timeout)
 88         self.connections.append(req)
 89         self.fds.append(req)
 90 
 91     def check_conn_timeout(self):
 92         """检查全部的请求,是否有已经链接超时,若是有则终止"""
 93         timeout_list = []
 94         for context in self.connections:
 95             if context.is_timeout():
 96                 timeout_list.append(context)
 97         for context in timeout_list:
 98             context.finish(AsyncTimeoutException('请求超时'))
 99             self.fds.remove(context)
100             self.connections.remove(context)
101 
102     def running(self):
103         """事件循环,用于检测请求的socket是否已经就绪,从而执行相关操做"""
104         while True:
105             r, w, e = select.select(self.fds, self.connections, self.fds, 0.05)
106 
107             if not self.fds:
108                 return
109 
110             for context in r:
111                 sock = context.sock
112                 while True:
113                     try:
114                         data = sock.recv(8096)
115                         if not data:
116                             self.fds.remove(context)
117                             context.finish()
118                             break
119                         else:
120                             context.write(data)
121                     except BlockingIOError as e:
122                         break
123                     except TimeoutError as e:
124                         self.fds.remove(context)
125                         self.connections.remove(context)
126                         context.finish(e)
127                         break
128 
129             for context in w:
130                 # 已经链接成功远程服务器,开始向远程发送请求数据
131                 if context in self.fds:
132                     data = context.send_request_data()
133                     context.sock.sendall(data)
134                     self.connections.remove(context)
135 
136             self.check_conn_timeout()
137 
138 
139 if __name__ == '__main__':
140     def callback_func(context, response, ex):
141         """
142         :param context: HttpContext对象,内部封装了请求相关信息
143         :param response: 请求响应内容
144         :param ex: 是否出现异常(若是有异常则值为异常对象;不然值为None)
145         :return:
146         """
147         print(context, response, ex)
148 
149     obj = AsyncRequest()
150     url_list = [
151         {'host': 'www.google.com', 'port': 80, 'method': 'GET', 'url': '/', 'data': '', 'timeout': 5,
152          'callback': callback_func},
153         {'host': 'www.baidu.com', 'port': 80, 'method': 'GET', 'url': '/', 'data': '', 'timeout': 5,
154          'callback': callback_func},
155         {'host': 'www.bing.com', 'port': 80, 'method': 'GET', 'url': '/', 'data': '', 'timeout': 5,
156          'callback': callback_func},
157     ]
158     for item in url_list:
159         print(item)
160         obj.add_request(**item)
161 
162     obj.running()
史上最牛逼的异步IO模块

Scrapy

Scrapy是一个为了爬取网站数据,提取结构性数据而编写的应用框架。 其能够应用在数据挖掘,信息处理或存储历史数据等一系列的程序中。
其最初是为了页面抓取 (更确切来讲, 网络抓取 )所设计的, 也能够应用在获取API所返回的数据(例如 Amazon Associates Web Services ) 或者通用的网络爬虫。Scrapy用途普遍,能够用于数据挖掘、监测和自动化测试。git

 

Scrapy 使用了 Twisted异步网络库来处理网络通信。总体架构大体以下:github

Scrapy主要包括了如下组件:web

  • 引擎(Scrapy)
    用来处理整个系统的数据流处理, 触发事务(框架核心)
  • 调度器(Scheduler)
    用来接受引擎发过来的请求, 压入队列中, 并在引擎再次请求的时候返回. 能够想像成一个URL(抓取网页的网址或者说是连接)的优先队列, 由它来决定下一个要抓取的网址是什么, 同时去除重复的网址
  • 下载器(Downloader)
    用于下载网页内容, 并将网页内容返回给蜘蛛(Scrapy下载器是创建在twisted这个高效的异步模型上的)
  • 爬虫(Spiders)
    爬虫是主要干活的, 用于从特定的网页中提取本身须要的信息, 即所谓的实体(Item)。用户也能够从中提取出连接,让Scrapy继续抓取下一个页面
  • 项目管道(Pipeline)
    负责处理爬虫从网页中抽取的实体,主要的功能是持久化实体、验证明体的有效性、清除不须要的信息。当页面被爬虫解析后,将被发送到项目管道,并通过几个特定的次序处理数据。
  • 下载器中间件(Downloader Middlewares)
    位于Scrapy引擎和下载器之间的框架,主要是处理Scrapy引擎与下载器之间的请求及响应。
  • 爬虫中间件(Spider Middlewares)
    介于Scrapy引擎和爬虫之间的框架,主要工做是处理蜘蛛的响应输入和请求输出。
  • 调度中间件(Scheduler Middewares)
    介于Scrapy引擎和调度之间的中间件,从Scrapy引擎发送到调度的请求和响应。

Scrapy运行流程大概以下:算法

  1. 引擎从调度器中取出一个连接(URL)用于接下来的抓取
  2. 引擎把URL封装成一个请求(Request)传给下载器
  3. 下载器把资源下载下来,并封装成应答包(Response)
  4. 爬虫解析Response
  5. 解析出实体(Item),则交给实体管道进行进一步的处理
  6. 解析出的是连接(URL),则把URL交给调度器等待抓取

1、安装json

 1 Linux
 2       pip3 install scrapy
 3  
 4  
 5 Windows
 6       a. pip3 install wheel
 7       b. 下载twisted http://www.lfd.uci.edu/~gohlke/pythonlibs/#twisted
 8       c. 进入下载目录,执行 pip3 install Twisted‑17.1.0‑cp35‑cp35m‑win_amd64.whl
 9       d. pip3 install scrapy
10       e. 下载并安装pywin32:https://sourceforge.net/projects/pywin32/files/

2、基本使用缓存

1. 基本命令服务器

 1 1. scrapy startproject 项目名称
 2    - 在当前目录中建立中建立一个项目文件(相似于Django)
 3  
 4 2. scrapy genspider [-t template] <name> <domain>
 5    - 建立爬虫应用
 6    如:
 7       scrapy gensipider -t basic oldboy oldboy.com
 8       scrapy gensipider -t xmlfeed autohome autohome.com.cn
 9    PS:
10       查看全部命令:scrapy gensipider -l
11       查看模板命令:scrapy gensipider -d 模板名称
12  
13 3. scrapy list
14    - 展现爬虫应用列表
15  
16 4. scrapy crawl 爬虫应用名称
17    - 运行单独爬虫应用

2.项目结构以及爬虫应用简介

 1 project_name/
 2    scrapy.cfg
 3    project_name/
 4        __init__.py
 5        items.py
 6        pipelines.py
 7        settings.py
 8        spiders/
 9            __init__.py
10            爬虫1.py
11            爬虫2.py
12            爬虫3.py

文件说明:

  • scrapy.cfg  项目的主配置信息。(真正爬虫相关的配置信息在settings.py文件中)
  • items.py    设置数据存储模板,用于结构化数据,如:Django的Model
  • pipelines    数据处理行为,如:通常结构化的数据持久化
  • settings.py 配置文件,如:递归的层数、并发数,延迟下载等
  • spiders      爬虫目录,如:建立文件,编写爬虫规则

注意:通常建立爬虫文件时,以网站域名命名

 1 import scrapy
 2  
 3 class XiaoHuarSpider(scrapy.spiders.Spider):
 4     name = "xiaohuar"                            # 爬虫名称 *****
 5     allowed_domains = ["xiaohuar.com"]  # 容许的域名
 6     start_urls = [
 7         "http://www.xiaohuar.com/hua/",   # 其实URL
 8     ]
 9  
10     def parse(self, response):
11         # 访问起始URL并获取结果后的回调函数
爬虫1.py

3. 小试牛刀

 1 import scrapy
 2 from scrapy.selector import HtmlXPathSelector
 3 from scrapy.http.request import Request
 4  
 5  
 6 class DigSpider(scrapy.Spider):
 7     # 爬虫应用的名称,经过此名称启动爬虫命令
 8     name = "dig"
 9  
10     # 容许的域名
11     allowed_domains = ["chouti.com"]
12  
13     # 起始URL
14     start_urls = [
15         'http://dig.chouti.com/',
16     ]
17  
18     has_request_set = {}
19  
20     def parse(self, response):
21         print(response.url)
22  
23         hxs = HtmlXPathSelector(response)
24         page_list = hxs.select('//div[@id="dig_lcpage"]//a[re:test(@href, "/all/hot/recent/\d+")]/@href').extract()
25         for page in page_list:
26             page_url = 'http://dig.chouti.com%s' % page
27             key = self.md5(page_url)
28             if key in self.has_request_set:
29                 pass
30             else:
31                 self.has_request_set[key] = page_url
32                 obj = Request(url=page_url, method='GET', callback=self.parse)
33                 yield obj
34  
35     @staticmethod
36     def md5(val):
37         import hashlib
38         ha = hashlib.md5()
39         ha.update(bytes(val, encoding='utf-8'))
40         key = ha.hexdigest()
41         return key
View Code

执行此爬虫文件,则在终端进入项目目录执行以下命令:

1 scrapy crawl dig --nolog

对于上述代码重要之处在于:

  • Request是一个封装用户请求的类,在回调函数中yield该对象表示继续访问
  • HtmlXpathSelector用于结构化HTML代码并提供选择器功能

4. 选择器

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 from scrapy.selector import Selector, HtmlXPathSelector
 4 from scrapy.http import HtmlResponse
 5 html = """<!DOCTYPE html>
 6 <html>
 7     <head lang="en">
 8         <meta charset="UTF-8">
 9         <title></title>
10     </head>
11     <body>
12         <ul>
13             <li class="item-"><a id='i1' href="link.html">first item</a></li>
14             <li class="item-0"><a id='i2' href="llink.html">first item</a></li>
15             <li class="item-1"><a href="llink2.html">second item<span>vv</span></a></li>
16         </ul>
17         <div><a href="llink2.html">second item</a></div>
18     </body>
19 </html>
20 """
21 response = HtmlResponse(url='http://example.com', body=html,encoding='utf-8')
22 # hxs = HtmlXPathSelector(response)
23 # print(hxs)
24 # hxs = Selector(response=response).xpath('//a')
25 # print(hxs)
26 # hxs = Selector(response=response).xpath('//a[2]')
27 # print(hxs)
28 # hxs = Selector(response=response).xpath('//a[@id]')
29 # print(hxs)
30 # hxs = Selector(response=response).xpath('//a[@id="i1"]')
31 # print(hxs)
32 # hxs = Selector(response=response).xpath('//a[@href="link.html"][@id="i1"]')
33 # print(hxs)
34 # hxs = Selector(response=response).xpath('//a[contains(@href, "link")]')
35 # print(hxs)
36 # hxs = Selector(response=response).xpath('//a[starts-with(@href, "link")]')
37 # print(hxs)
38 # hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]')
39 # print(hxs)
40 # hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/text()').extract()
41 # print(hxs)
42 # hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/@href').extract()
43 # print(hxs)
44 # hxs = Selector(response=response).xpath('/html/body/ul/li/a/@href').extract()
45 # print(hxs)
46 # hxs = Selector(response=response).xpath('//body/ul/li/a/@href').extract_first()
47 # print(hxs)
48  
49 # ul_list = Selector(response=response).xpath('//body/ul/li')
50 # for item in ul_list:
51 #     v = item.xpath('./a/span')
52 #     # 或
53 #     # v = item.xpath('a/span')
54 #     # 或
55 #     # v = item.xpath('*/a/span')
56 #     print(v)
View Code
 1 # -*- coding: utf-8 -*-
 2 import scrapy
 3 from scrapy.selector import HtmlXPathSelector
 4 from scrapy.http.request import Request
 5 from scrapy.http.cookies import CookieJar
 6 from scrapy import FormRequest
 7 
 8 
 9 class ChouTiSpider(scrapy.Spider):
10     # 爬虫应用的名称,经过此名称启动爬虫命令
11     name = "chouti"
12     # 容许的域名
13     allowed_domains = ["chouti.com"]
14 
15     cookie_dict = {}
16     has_request_set = {}
17 
18     def start_requests(self):
19         url = 'http://dig.chouti.com/'
20         # return [Request(url=url, callback=self.login)]
21         yield Request(url=url, callback=self.login)
22 
23     def login(self, response):
24         cookie_jar = CookieJar()
25         cookie_jar.extract_cookies(response, response.request)
26         for k, v in cookie_jar._cookies.items():
27             for i, j in v.items():
28                 for m, n in j.items():
29                     self.cookie_dict[m] = n.value
30 
31         req = Request(
32             url='http://dig.chouti.com/login',
33             method='POST',
34             headers={'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8'},
35             body='phone=8615131255089&password=pppppppp&oneMonth=1',
36             cookies=self.cookie_dict,
37             callback=self.check_login
38         )
39         yield req
40 
41     def check_login(self, response):
42         req = Request(
43             url='http://dig.chouti.com/',
44             method='GET',
45             callback=self.show,
46             cookies=self.cookie_dict,
47             dont_filter=True
48         )
49         yield req
50 
51     def show(self, response):
52         # print(response)
53         hxs = HtmlXPathSelector(response)
54         news_list = hxs.select('//div[@id="content-list"]/div[@class="item"]')
55         for new in news_list:
56             # temp = new.xpath('div/div[@class="part2"]/@share-linkid').extract()
57             link_id = new.xpath('*/div[@class="part2"]/@share-linkid').extract_first()
58             yield Request(
59                 url='http://dig.chouti.com/link/vote?linksId=%s' %(link_id,),
60                 method='POST',
61                 cookies=self.cookie_dict,
62                 callback=self.do_favor
63             )
64 
65         page_list = hxs.select('//div[@id="dig_lcpage"]//a[re:test(@href, "/all/hot/recent/\d+")]/@href').extract()
66         for page in page_list:
67 
68             page_url = 'http://dig.chouti.com%s' % page
69             import hashlib
70             hash = hashlib.md5()
71             hash.update(bytes(page_url,encoding='utf-8'))
72             key = hash.hexdigest()
73             if key in self.has_request_set:
74                 pass
75             else:
76                 self.has_request_set[key] = page_url
77                 yield Request(
78                     url=page_url,
79                     method='GET',
80                     callback=self.show
81                 )
82 
83     def do_favor(self, response):
84         print(response.text)
示例:自动登录抽屉并点赞

注意:settings.py中设置DEPTH_LIMIT = 1来指定“递归”的层数。

5. 格式化处理

上述实例只是简单的处理,因此在parse方法中直接处理。若是对于想要获取更多的数据处理,则能够利用Scrapy的items将数据格式化,而后统一交由pipelines来处理。

 1 import scrapy
 2 from scrapy.selector import HtmlXPathSelector
 3 from scrapy.http.request import Request
 4 from scrapy.http.cookies import CookieJar
 5 from scrapy import FormRequest
 6 
 7 
 8 class XiaoHuarSpider(scrapy.Spider):
 9     # 爬虫应用的名称,经过此名称启动爬虫命令
10     name = "xiaohuar"
11     # 容许的域名
12     allowed_domains = ["xiaohuar.com"]
13 
14     start_urls = [
15         "http://www.xiaohuar.com/list-1-1.html",
16     ]
17     # custom_settings = {
18     #     'ITEM_PIPELINES':{
19     #         'spider1.pipelines.JsonPipeline': 100
20     #     }
21     # }
22     has_request_set = {}
23 
24     def parse(self, response):
25         # 分析页面
26         # 找到页面中符合规则的内容(校花图片),保存
27         # 找到全部的a标签,再访问其余a标签,一层一层的搞下去
28 
29         hxs = HtmlXPathSelector(response)
30 
31         items = hxs.select('//div[@class="item_list infinite_scroll"]/div')
32         for item in items:
33             src = item.select('.//div[@class="img"]/a/img/@src').extract_first()
34             name = item.select('.//div[@class="img"]/span/text()').extract_first()
35             school = item.select('.//div[@class="img"]/div[@class="btns"]/a/text()').extract_first()
36             url = "http://www.xiaohuar.com%s" % src
37             from ..items import XiaoHuarItem
38             obj = XiaoHuarItem(name=name, school=school, url=url)
39             yield obj
40 
41         urls = hxs.select('//a[re:test(@href, "http://www.xiaohuar.com/list-1-\d+.html")]/@href')
42         for url in urls:
43             key = self.md5(url)
44             if key in self.has_request_set:
45                 pass
46             else:
47                 self.has_request_set[key] = url
48                 req = Request(url=url,method='GET',callback=self.parse)
49                 yield req
50 
51     @staticmethod
52     def md5(val):
53         import hashlib
54         ha = hashlib.md5()
55         ha.update(bytes(val, encoding='utf-8'))
56         key = ha.hexdigest()
57         return key
spiders/xiahuar.py
1 import scrapy
2 
3 
4 class XiaoHuarItem(scrapy.Item):
5     name = scrapy.Field()
6     school = scrapy.Field()
7     url = scrapy.Field()
items
 1 import json
 2 import os
 3 import requests
 4 
 5 
 6 class JsonPipeline(object):
 7     def __init__(self):
 8         self.file = open('xiaohua.txt', 'w')
 9 
10     def process_item(self, item, spider):
11         v = json.dumps(dict(item), ensure_ascii=False)
12         self.file.write(v)
13         self.file.write('\n')
14         self.file.flush()
15         return item
16 
17 
18 class FilePipeline(object):
19     def __init__(self):
20         if not os.path.exists('imgs'):
21             os.makedirs('imgs')
22 
23     def process_item(self, item, spider):
24         response = requests.get(item['url'], stream=True)
25         file_name = '%s_%s.jpg' % (item['name'], item['school'])
26         with open(os.path.join('imgs', file_name), mode='wb') as f:
27             f.write(response.content)
28         return item
pipelines
1 ITEM_PIPELINES = {
2    'spider1.pipelines.JsonPipeline': 100,
3    'spider1.pipelines.FilePipeline': 300,
4 }
5 # 每行后面的整型值,肯定了他们运行的顺序,item按数字从低到高的顺序,经过pipeline,一般将这些数字定义在0-1000范围内。
settings

对于pipeline能够作更多,以下:

 1 from scrapy.exceptions import DropItem
 2 
 3 class CustomPipeline(object):
 4     def __init__(self,v):
 5         self.value = v
 6 
 7     def process_item(self, item, spider):
 8         # 操做并进行持久化
 9 
10         # return表示会被后续的pipeline继续处理
11         return item
12 
13         # 表示将item丢弃,不会被后续pipeline处理
14         # raise DropItem()
15 
16 
17     @classmethod
18     def from_crawler(cls, crawler):
19         """
20         初始化时候,用于建立pipeline对象
21         :param crawler: 
22         :return: 
23         """
24         val = crawler.settings.getint('MMMM')
25         return cls(val)
26 
27     def open_spider(self,spider):
28         """
29         爬虫开始执行时,调用
30         :param spider: 
31         :return: 
32         """
33         print('000000')
34 
35     def close_spider(self,spider):
36         """
37         爬虫关闭时,被调用
38         :param spider: 
39         :return: 
40         """
41         print('111111')
自定义pipeline

6.中间件

 1 class SpiderMiddleware(object):
 2 
 3     def process_spider_input(self,response, spider):
 4         """
 5         下载完成,执行,而后交给parse处理
 6         :param response: 
 7         :param spider: 
 8         :return: 
 9         """
10         pass
11 
12     def process_spider_output(self,response, result, spider):
13         """
14         spider处理完成,返回时调用
15         :param response:
16         :param result:
17         :param spider:
18         :return: 必须返回包含 Request 或 Item 对象的可迭代对象(iterable)
19         """
20         return result
21 
22     def process_spider_exception(self,response, exception, spider):
23         """
24         异常调用
25         :param response:
26         :param exception:
27         :param spider:
28         :return: None,继续交给后续中间件处理异常;含 Response 或 Item 的可迭代对象(iterable),交给调度器或pipeline
29         """
30         return None
31 
32 
33     def process_start_requests(self,start_requests, spider):
34         """
35         爬虫启动时调用
36         :param start_requests:
37         :param spider:
38         :return: 包含 Request 对象的可迭代对象
39         """
40         return start_requests
爬虫中间件
 1 class DownMiddleware1(object):
 2     def process_request(self, request, spider):
 3         """
 4         请求须要被下载时,通过全部下载器中间件的process_request调用
 5         :param request: 
 6         :param spider: 
 7         :return:  
 8             None,继续后续中间件去下载;
 9             Response对象,中止process_request的执行,开始执行process_response
10             Request对象,中止中间件的执行,将Request从新调度器
11             raise IgnoreRequest异常,中止process_request的执行,开始执行process_exception
12         """
13         pass
14 
15 
16 
17     def process_response(self, request, response, spider):
18         """
19         spider处理完成,返回时调用
20         :param response:
21         :param result:
22         :param spider:
23         :return: 
24             Response 对象:转交给其余中间件process_response
25             Request 对象:中止中间件,request会被从新调度下载
26             raise IgnoreRequest 异常:调用Request.errback
27         """
28         print('response1')
29         return response
30 
31     def process_exception(self, request, exception, spider):
32         """
33         当下载处理器(download handler)或 process_request() (下载中间件)抛出异常
34         :param response:
35         :param exception:
36         :param spider:
37         :return: 
38             None:继续交给后续中间件处理异常;
39             Response对象:中止后续process_exception方法
40             Request对象:中止中间件,request将会被从新调用下载
41         """
42         return None
下载器中间件

7. 自定制命令

  • 在spiders同级建立任意目录,如:commands
  • 在其中建立 crawlall.py 文件 (此处文件名就是自定义的命令)
 1 from scrapy.commands import ScrapyCommand
 2     from scrapy.utils.project import get_project_settings
 3 
 4 
 5     class Command(ScrapyCommand):
 6 
 7         requires_project = True
 8 
 9         def syntax(self):
10             return '[options]'
11 
12         def short_desc(self):
13             return 'Runs all of the spiders'
14 
15         def run(self, args, opts):
16             spider_list = self.crawler_process.spiders.list()
17             for name in spider_list:
18                 self.crawler_process.crawl(name, **opts.__dict__)
19             self.crawler_process.start()
crawlall.py
  • 在settings.py 中添加配置 COMMANDS_MODULE = '项目名称.目录名称'
  • 在项目目录执行命令:scrapy crawlall 

8. 自定义扩展

自定义扩展时,利用信号在指定位置注册制定操做

 1 from scrapy import signals
 2 
 3 
 4 class MyExtension(object):
 5     def __init__(self, value):
 6         self.value = value
 7 
 8     @classmethod
 9     def from_crawler(cls, crawler):
10         val = crawler.settings.getint('MMMM')
11         ext = cls(val)
12 
13         crawler.signals.connect(ext.spider_opened, signal=signals.spider_opened)
14         crawler.signals.connect(ext.spider_closed, signal=signals.spider_closed)
15 
16         return ext
17 
18     def spider_opened(self, spider):
19         print('open')
20 
21     def spider_closed(self, spider):
22         print('close')
View Code

9. 避免重复访问

scrapy默认使用 scrapy.dupefilter.RFPDupeFilter 进行去重,相关配置有:

1 DUPEFILTER_CLASS = 'scrapy.dupefilter.RFPDupeFilter'
2 DUPEFILTER_DEBUG = False
3 JOBDIR = "保存范文记录的日志路径,如:/root/"  # 最终路径为 /root/requests.seen
 1 class RepeatUrl:
 2     def __init__(self):
 3         self.visited_url = set()
 4 
 5     @classmethod
 6     def from_settings(cls, settings):
 7         """
 8         初始化时,调用
 9         :param settings: 
10         :return: 
11         """
12         return cls()
13 
14     def request_seen(self, request):
15         """
16         检测当前请求是否已经被访问过
17         :param request: 
18         :return: True表示已经访问过;False表示未访问过
19         """
20         if request.url in self.visited_url:
21             return True
22         self.visited_url.add(request.url)
23         return False
24 
25     def open(self):
26         """
27         开始爬去请求时,调用
28         :return: 
29         """
30         print('open replication')
31 
32     def close(self, reason):
33         """
34         结束爬虫爬取时,调用
35         :param reason: 
36         :return: 
37         """
38         print('close replication')
39 
40     def log(self, request, spider):
41         """
42         记录日志
43         :param request: 
44         :param spider: 
45         :return: 
46         """
47         print('repeat', request.url)
自定义URL去重操做

10.其余

  1 # -*- coding: utf-8 -*-
  2 
  3 # Scrapy settings for step8_king project
  4 #
  5 # For simplicity, this file contains only settings considered important or
  6 # commonly used. You can find more settings consulting the documentation:
  7 #
  8 #     http://doc.scrapy.org/en/latest/topics/settings.html
  9 #     http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
 10 #     http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
 11 
 12 # 1. 爬虫名称
 13 BOT_NAME = 'step8_king'
 14 
 15 # 2. 爬虫应用路径
 16 SPIDER_MODULES = ['step8_king.spiders']
 17 NEWSPIDER_MODULE = 'step8_king.spiders'
 18 
 19 # Crawl responsibly by identifying yourself (and your website) on the user-agent
 20 # 3. 客户端 user-agent请求头
 21 # USER_AGENT = 'step8_king (+http://www.yourdomain.com)'
 22 
 23 # Obey robots.txt rules
 24 # 4. 禁止爬虫配置
 25 # ROBOTSTXT_OBEY = False
 26 
 27 # Configure maximum concurrent requests performed by Scrapy (default: 16)
 28 # 5. 并发请求数
 29 # CONCURRENT_REQUESTS = 4
 30 
 31 # Configure a delay for requests for the same website (default: 0)
 32 # See http://scrapy.readthedocs.org/en/latest/topics/settings.html#download-delay
 33 # See also autothrottle settings and docs
 34 # 6. 延迟下载秒数
 35 # DOWNLOAD_DELAY = 2
 36 
 37 
 38 # The download delay setting will honor only one of:
 39 # 7. 单域名访问并发数,而且延迟下次秒数也应用在每一个域名
 40 # CONCURRENT_REQUESTS_PER_DOMAIN = 2
 41 # 单IP访问并发数,若是有值则忽略:CONCURRENT_REQUESTS_PER_DOMAIN,而且延迟下次秒数也应用在每一个IP
 42 # CONCURRENT_REQUESTS_PER_IP = 3
 43 
 44 # Disable cookies (enabled by default)
 45 # 8. 是否支持cookie,cookiejar进行操做cookie
 46 # COOKIES_ENABLED = True
 47 # COOKIES_DEBUG = True
 48 
 49 # Disable Telnet Console (enabled by default)
 50 # 9. Telnet用于查看当前爬虫的信息,操做爬虫等...
 51 #    使用telnet ip port ,而后经过命令操做
 52 # TELNETCONSOLE_ENABLED = True
 53 # TELNETCONSOLE_HOST = '127.0.0.1'
 54 # TELNETCONSOLE_PORT = [6023,]
 55 
 56 
 57 # 10. 默认请求头
 58 # Override the default request headers:
 59 # DEFAULT_REQUEST_HEADERS = {
 60 #     'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
 61 #     'Accept-Language': 'en',
 62 # }
 63 
 64 
 65 # Configure item pipelines
 66 # See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
 67 # 11. 定义pipeline处理请求
 68 # ITEM_PIPELINES = {
 69 #    'step8_king.pipelines.JsonPipeline': 700,
 70 #    'step8_king.pipelines.FilePipeline': 500,
 71 # }
 72 
 73 
 74 
 75 # 12. 自定义扩展,基于信号进行调用
 76 # Enable or disable extensions
 77 # See http://scrapy.readthedocs.org/en/latest/topics/extensions.html
 78 # EXTENSIONS = {
 79 #     # 'step8_king.extensions.MyExtension': 500,
 80 # }
 81 
 82 
 83 # 13. 爬虫容许的最大深度,能够经过meta查看当前深度;0表示无深度
 84 # DEPTH_LIMIT = 3
 85 
 86 # 14. 爬取时,0表示深度优先Lifo(默认);1表示广度优先FiFo
 87 
 88 # 后进先出,深度优先
 89 # DEPTH_PRIORITY = 0
 90 # SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleLifoDiskQueue'
 91 # SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.LifoMemoryQueue'
 92 # 先进先出,广度优先
 93 
 94 # DEPTH_PRIORITY = 1
 95 # SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleFifoDiskQueue'
 96 # SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.FifoMemoryQueue'
 97 
 98 # 15. 调度器队列
 99 # SCHEDULER = 'scrapy.core.scheduler.Scheduler'
100 # from scrapy.core.scheduler import Scheduler
101 
102 
103 # 16. 访问URL去重
104 # DUPEFILTER_CLASS = 'step8_king.duplication.RepeatUrl'
105 
106 
107 # Enable and configure the AutoThrottle extension (disabled by default)
108 # See http://doc.scrapy.org/en/latest/topics/autothrottle.html
109 
110 """
111 17. 自动限速算法
112     from scrapy.contrib.throttle import AutoThrottle
113     自动限速设置
114     1. 获取最小延迟 DOWNLOAD_DELAY
115     2. 获取最大延迟 AUTOTHROTTLE_MAX_DELAY
116     3. 设置初始下载延迟 AUTOTHROTTLE_START_DELAY
117     4. 当请求下载完成后,获取其"链接"时间 latency,即:请求链接到接受到响应头之间的时间
118     5. 用于计算的... AUTOTHROTTLE_TARGET_CONCURRENCY
119     target_delay = latency / self.target_concurrency
120     new_delay = (slot.delay + target_delay) / 2.0 # 表示上一次的延迟时间
121     new_delay = max(target_delay, new_delay)
122     new_delay = min(max(self.mindelay, new_delay), self.maxdelay)
123     slot.delay = new_delay
124 """
125 
126 # 开始自动限速
127 # AUTOTHROTTLE_ENABLED = True
128 # The initial download delay
129 # 初始下载延迟
130 # AUTOTHROTTLE_START_DELAY = 5
131 # The maximum download delay to be set in case of high latencies
132 # 最大下载延迟
133 # AUTOTHROTTLE_MAX_DELAY = 10
134 # The average number of requests Scrapy should be sending in parallel to each remote server
135 # 平均每秒并发数
136 # AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
137 
138 # Enable showing throttling stats for every response received:
139 # 是否显示
140 # AUTOTHROTTLE_DEBUG = True
141 
142 # Enable and configure HTTP caching (disabled by default)
143 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
144 
145 
146 """
147 18. 启用缓存
148     目的用于将已经发送的请求或相应缓存下来,以便之后使用
149     
150     from scrapy.downloadermiddlewares.httpcache import HttpCacheMiddleware
151     from scrapy.extensions.httpcache import DummyPolicy
152     from scrapy.extensions.httpcache import FilesystemCacheStorage
153 """
154 # 是否启用缓存策略
155 # HTTPCACHE_ENABLED = True
156 
157 # 缓存策略:全部请求均缓存,下次在请求直接访问原来的缓存便可
158 # HTTPCACHE_POLICY = "scrapy.extensions.httpcache.DummyPolicy"
159 # 缓存策略:根据Http响应头:Cache-Control、Last-Modified 等进行缓存的策略
160 # HTTPCACHE_POLICY = "scrapy.extensions.httpcache.RFC2616Policy"
161 
162 # 缓存超时时间
163 # HTTPCACHE_EXPIRATION_SECS = 0
164 
165 # 缓存保存路径
166 # HTTPCACHE_DIR = 'httpcache'
167 
168 # 缓存忽略的Http状态码
169 # HTTPCACHE_IGNORE_HTTP_CODES = []
170 
171 # 缓存存储的插件
172 # HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'
173 
174 
175 """
176 19. 代理,须要在环境变量中设置
177     from scrapy.contrib.downloadermiddleware.httpproxy import HttpProxyMiddleware
178     
179     方式一:使用默认
180         os.environ
181         {
182             http_proxy:http://root:woshiniba@192.168.11.11:9999/
183             https_proxy:http://192.168.11.11:9999/
184         }
185     方式二:使用自定义下载中间件
186     
187     def to_bytes(text, encoding=None, errors='strict'):
188         if isinstance(text, bytes):
189             return text
190         if not isinstance(text, six.string_types):
191             raise TypeError('to_bytes must receive a unicode, str or bytes '
192                             'object, got %s' % type(text).__name__)
193         if encoding is None:
194             encoding = 'utf-8'
195         return text.encode(encoding, errors)
196         
197     class ProxyMiddleware(object):
198         def process_request(self, request, spider):
199             PROXIES = [
200                 {'ip_port': '111.11.228.75:80', 'user_pass': ''},
201                 {'ip_port': '120.198.243.22:80', 'user_pass': ''},
202                 {'ip_port': '111.8.60.9:8123', 'user_pass': ''},
203                 {'ip_port': '101.71.27.120:80', 'user_pass': ''},
204                 {'ip_port': '122.96.59.104:80', 'user_pass': ''},
205                 {'ip_port': '122.224.249.122:8088', 'user_pass': ''},
206             ]
207             proxy = random.choice(PROXIES)
208             if proxy['user_pass'] is not None:
209                 request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
210                 encoded_user_pass = base64.encodestring(to_bytes(proxy['user_pass']))
211                 request.headers['Proxy-Authorization'] = to_bytes('Basic ' + encoded_user_pass)
212                 print "**************ProxyMiddleware have pass************" + proxy['ip_port']
213             else:
214                 print "**************ProxyMiddleware no pass************" + proxy['ip_port']
215                 request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
216     
217     DOWNLOADER_MIDDLEWARES = {
218        'step8_king.middlewares.ProxyMiddleware': 500,
219     }
220     
221 """
222 
223 """
224 20. Https访问
225     Https访问时有两种状况:
226     1. 要爬取网站使用的可信任证书(默认支持)
227         DOWNLOADER_HTTPCLIENTFACTORY = "scrapy.core.downloader.webclient.ScrapyHTTPClientFactory"
228         DOWNLOADER_CLIENTCONTEXTFACTORY = "scrapy.core.downloader.contextfactory.ScrapyClientContextFactory"
229         
230     2. 要爬取网站使用的自定义证书
231         DOWNLOADER_HTTPCLIENTFACTORY = "scrapy.core.downloader.webclient.ScrapyHTTPClientFactory"
232         DOWNLOADER_CLIENTCONTEXTFACTORY = "step8_king.https.MySSLFactory"
233         
234         # https.py
235         from scrapy.core.downloader.contextfactory import ScrapyClientContextFactory
236         from twisted.internet.ssl import (optionsForClientTLS, CertificateOptions, PrivateCertificate)
237         
238         class MySSLFactory(ScrapyClientContextFactory):
239             def getCertificateOptions(self):
240                 from OpenSSL import crypto
241                 v1 = crypto.load_privatekey(crypto.FILETYPE_PEM, open('/Users/wupeiqi/client.key.unsecure', mode='r').read())
242                 v2 = crypto.load_certificate(crypto.FILETYPE_PEM, open('/Users/wupeiqi/client.pem', mode='r').read())
243                 return CertificateOptions(
244                     privateKey=v1,  # pKey对象
245                     certificate=v2,  # X509对象
246                     verify=False,
247                     method=getattr(self, 'method', getattr(self, '_ssl_method', None))
248                 )
249     其余:
250         相关类
251             scrapy.core.downloader.handlers.http.HttpDownloadHandler
252             scrapy.core.downloader.webclient.ScrapyHTTPClientFactory
253             scrapy.core.downloader.contextfactory.ScrapyClientContextFactory
254         相关配置
255             DOWNLOADER_HTTPCLIENTFACTORY
256             DOWNLOADER_CLIENTCONTEXTFACTORY
257 
258 """
259 
260 
261 
262 """
263 21. 爬虫中间件
264     class SpiderMiddleware(object):
265 
266         def process_spider_input(self,response, spider):
267             '''
268             下载完成,执行,而后交给parse处理
269             :param response: 
270             :param spider: 
271             :return: 
272             '''
273             pass
274     
275         def process_spider_output(self,response, result, spider):
276             '''
277             spider处理完成,返回时调用
278             :param response:
279             :param result:
280             :param spider:
281             :return: 必须返回包含 Request 或 Item 对象的可迭代对象(iterable)
282             '''
283             return result
284     
285         def process_spider_exception(self,response, exception, spider):
286             '''
287             异常调用
288             :param response:
289             :param exception:
290             :param spider:
291             :return: None,继续交给后续中间件处理异常;含 Response 或 Item 的可迭代对象(iterable),交给调度器或pipeline
292             '''
293             return None
294     
295     
296         def process_start_requests(self,start_requests, spider):
297             '''
298             爬虫启动时调用
299             :param start_requests:
300             :param spider:
301             :return: 包含 Request 对象的可迭代对象
302             '''
303             return start_requests
304     
305     内置爬虫中间件:
306         'scrapy.contrib.spidermiddleware.httperror.HttpErrorMiddleware': 50,
307         'scrapy.contrib.spidermiddleware.offsite.OffsiteMiddleware': 500,
308         'scrapy.contrib.spidermiddleware.referer.RefererMiddleware': 700,
309         'scrapy.contrib.spidermiddleware.urllength.UrlLengthMiddleware': 800,
310         'scrapy.contrib.spidermiddleware.depth.DepthMiddleware': 900,
311 
312 """
313 # from scrapy.contrib.spidermiddleware.referer import RefererMiddleware
314 # Enable or disable spider middlewares
315 # See http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
316 SPIDER_MIDDLEWARES = {
317    # 'step8_king.middlewares.SpiderMiddleware': 543,
318 }
319 
320 
321 """
322 22. 下载中间件
323     class DownMiddleware1(object):
324         def process_request(self, request, spider):
325             '''
326             请求须要被下载时,通过全部下载器中间件的process_request调用
327             :param request:
328             :param spider:
329             :return:
330                 None,继续后续中间件去下载;
331                 Response对象,中止process_request的执行,开始执行process_response
332                 Request对象,中止中间件的执行,将Request从新调度器
333                 raise IgnoreRequest异常,中止process_request的执行,开始执行process_exception
334             '''
335             pass
336     
337     
338     
339         def process_response(self, request, response, spider):
340             '''
341             spider处理完成,返回时调用
342             :param response:
343             :param result:
344             :param spider:
345             :return:
346                 Response 对象:转交给其余中间件process_response
347                 Request 对象:中止中间件,request会被从新调度下载
348                 raise IgnoreRequest 异常:调用Request.errback
349             '''
350             print('response1')
351             return response
352     
353         def process_exception(self, request, exception, spider):
354             '''
355             当下载处理器(download handler)或 process_request() (下载中间件)抛出异常
356             :param response:
357             :param exception:
358             :param spider:
359             :return:
360                 None:继续交给后续中间件处理异常;
361                 Response对象:中止后续process_exception方法
362                 Request对象:中止中间件,request将会被从新调用下载
363             '''
364             return None
365 
366     
367     默认下载中间件
368     {
369         'scrapy.contrib.downloadermiddleware.robotstxt.RobotsTxtMiddleware': 100,
370         'scrapy.contrib.downloadermiddleware.httpauth.HttpAuthMiddleware': 300,
371         'scrapy.contrib.downloadermiddleware.downloadtimeout.DownloadTimeoutMiddleware': 350,
372         'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': 400,
373         'scrapy.contrib.downloadermiddleware.retry.RetryMiddleware': 500,
374         'scrapy.contrib.downloadermiddleware.defaultheaders.DefaultHeadersMiddleware': 550,
375         'scrapy.contrib.downloadermiddleware.redirect.MetaRefreshMiddleware': 580,
376         'scrapy.contrib.downloadermiddleware.httpcompression.HttpCompressionMiddleware': 590,
377         'scrapy.contrib.downloadermiddleware.redirect.RedirectMiddleware': 600,
378         'scrapy.contrib.downloadermiddleware.cookies.CookiesMiddleware': 700,
379         'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 750,
380         'scrapy.contrib.downloadermiddleware.chunked.ChunkedTransferMiddleware': 830,
381         'scrapy.contrib.downloadermiddleware.stats.DownloaderStats': 850,
382         'scrapy.contrib.downloadermiddleware.httpcache.HttpCacheMiddleware': 900,
383     }
384 
385 """
386 # from scrapy.contrib.downloadermiddleware.httpauth import HttpAuthMiddleware
387 # Enable or disable downloader middlewares
388 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
389 # DOWNLOADER_MIDDLEWARES = {
390 #    'step8_king.middlewares.DownMiddleware1': 100,
391 #    'step8_king.middlewares.DownMiddleware2': 500,
392 # }
settings

11.TinyScrapy

  1 #!/usr/bin/env python
  2 # -*- coding:utf-8 -*-
  3 import types
  4 from twisted.internet import defer
  5 from twisted.web.client import getPage
  6 from twisted.internet import reactor
  7 
  8 
  9 
 10 class Request(object):
 11     def __init__(self, url, callback):
 12         self.url = url
 13         self.callback = callback
 14         self.priority = 0
 15 
 16 
 17 class HttpResponse(object):
 18     def __init__(self, content, request):
 19         self.content = content
 20         self.request = request
 21 
 22 
 23 class ChouTiSpider(object):
 24 
 25     def start_requests(self):
 26         url_list = ['http://www.cnblogs.com/', 'http://www.bing.com']
 27         for url in url_list:
 28             yield Request(url=url, callback=self.parse)
 29 
 30     def parse(self, response):
 31         print(response.request.url)
 32         # yield Request(url="http://www.baidu.com", callback=self.parse)
 33 
 34 
 35 
 36 
 37 from queue import Queue
 38 Q = Queue()
 39 
 40 
 41 class CallLaterOnce(object):
 42     def __init__(self, func, *a, **kw):
 43         self._func = func
 44         self._a = a
 45         self._kw = kw
 46         self._call = None
 47 
 48     def schedule(self, delay=0):
 49         if self._call is None:
 50             self._call = reactor.callLater(delay, self)
 51 
 52     def cancel(self):
 53         if self._call:
 54             self._call.cancel()
 55 
 56     def __call__(self):
 57         self._call = None
 58         return self._func(*self._a, **self._kw)
 59 
 60 
 61 class Engine(object):
 62     def __init__(self):
 63         self.nextcall = None
 64         self.crawlling = []
 65         self.max = 5
 66         self._closewait = None
 67 
 68     def get_response(self,content, request):
 69         response = HttpResponse(content, request)
 70         gen = request.callback(response)
 71         if isinstance(gen, types.GeneratorType):
 72             for req in gen:
 73                 req.priority = request.priority + 1
 74                 Q.put(req)
 75 
 76 
 77     def rm_crawlling(self,response,d):
 78         self.crawlling.remove(d)
 79 
 80     def _next_request(self,spider):
 81         if Q.qsize() == 0 and len(self.crawlling) == 0:
 82             self._closewait.callback(None)
 83 
 84         if len(self.crawlling) >= 5:
 85             return
 86         while len(self.crawlling) < 5:
 87             try:
 88                 req = Q.get(block=False)
 89             except Exception as e:
 90                 req = None
 91             if not req:
 92                 return
 93             d = getPage(req.url.encode('utf-8'))
 94             self.crawlling.append(d)
 95             d.addCallback(self.get_response, req)
 96             d.addCallback(self.rm_crawlling,d)
 97             d.addCallback(lambda _: self.nextcall.schedule())
 98 
 99 
100     @defer.inlineCallbacks
101     def crawl(self):
102         spider = ChouTiSpider()
103         start_requests = iter(spider.start_requests())
104         flag = True
105         while flag:
106             try:
107                 req = next(start_requests)
108                 Q.put(req)
109             except StopIteration as e:
110                 flag = False
111 
112         self.nextcall = CallLaterOnce(self._next_request,spider)
113         self.nextcall.schedule()
114 
115         self._closewait = defer.Deferred()
116         yield self._closewait
117 
118     @defer.inlineCallbacks
119     def pp(self):
120         yield self.crawl()
121 
122 _active = set()
123 obj = Engine()
124 d = obj.crawl()
125 _active.add(d)
126 
127 li = defer.DeferredList(_active)
128 li.addBoth(lambda _,*a,**kw: reactor.stop())
129 
130 reactor.run()
参考版 

更多文档参见:http://scrapy-chs.readthedocs.io/zh_CN/latest/index.html

 

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