性能相关的了解
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时必然会引起等待，从而使得请求整体变慢。如下各种不同的执行
import requests def fetch_async(url): response = requests.get(url) return response url_list = ['http://www.github.com', 'http://www.bing.com'] for url in url_list: fetch_async(url)
from concurrent.futures import ThreadPoolExecutor import requests def fetch_async(url): response = requests.get(url) return response url_list = ['http://www.github.com', 'http://www.bing.com'] pool = ThreadPoolExecutor(5) for url in url_list: pool.submit(fetch_async, url) pool.shutdown(wait=True)
from concurrent.futures import ThreadPoolExecutor import requests def fetch_async(url): response = requests.get(url) return response def callback(future): print(future.result()) url_list = ['http://www.github.com', 'http://www.bing.com'] pool = ThreadPoolExecutor(5) for url in url_list: v = pool.submit(fetch_async, url) v.add_done_callback(callback) pool.shutdown(wait=True)
from concurrent.futures import ProcessPoolExecutor import requests def fetch_async(url): response = requests.get(url) return response def callback(future): print(future.result()) url_list = ['http://www.github.com', 'http://www.bing.com'] pool = ProcessPoolExecutor(5) for url in url_list: v = pool.submit(fetch_async, url) v.add_done_callback(callback) pool.shutdown(wait=True)
通过上述代码均可以完成对请求性能的提高，对于多线程和多进行的缺点是在IO阻塞时会造成了线程和进程的浪费，所以异步IO会是首选，通常的异步io模型如下：
import asyncio @asyncio.coroutine def func1(): print('before...func1......') yield from asyncio.sleep(5) print('end...func1......') tasks = [func1(), func1()] loop = asyncio.get_event_loop() loop.run_until_complete(asyncio.gather(*tasks)) loop.close()
#只能基于发tcp请求
import asyncio @asyncio.coroutine def fetch_async(host, url='/'): print(host, url) reader, writer = yield from asyncio.open_connection(host, 80) request_header_content = """GET %s HTTP/1.0\r\nHost: %s\r\n\r\n""" % (url, host,) request_header_content = bytes(request_header_content, encoding='utf-8') writer.write(request_header_content) yield from writer.drain() text = yield from reader.read() print(host, url, text) writer.close() tasks = [ fetch_async('www.cnblogs.com', '/wupeiqi/'), fetch_async('dig.chouti.com', '/pic/show?nid=4073644713430508&lid=10273091') ] loop = asyncio.get_event_loop() results = loop.run_until_complete(asyncio.gather(*tasks)) loop.close()
import aiohttp import asyncio @asyncio.coroutine def fetch_async(url): print(url) response = yield from aiohttp.request('GET', url) # data = yield from response.read() # print(url, data) print(url, response) response.close() tasks = [fetch_async('http://www.google.com/'), fetch_async('http://www.chouti.com/')] event_loop = asyncio.get_event_loop() results = event_loop.run_until_complete(asyncio.gather(*tasks)) event_loop.close()
import asyncio import requests @asyncio.coroutine def fetch_async(func, *args): loop = asyncio.get_event_loop() future = loop.run_in_executor(None, func, *args) response = yield from future print(response.url, response.content) tasks = [ fetch_async(requests.get, 'http://www.cnblogs.com/wupeiqi/'), fetch_async(requests.get, 'http://dig.chouti.com/pic/show?nid=4073644713430508&lid=10273091') ] loop = asyncio.get_event_loop() results = loop.run_until_complete(asyncio.gather(*tasks)) loop.close()
import gevent import requests from gevent import monkey monkey.patch_all() def fetch_async(method, url, req_kwargs): print(method, url, req_kwargs) response = requests.request(method=method, url=url, **req_kwargs) print(response.url, response.content) # ##### 发送请求 ##### gevent.joinall([ gevent.spawn(fetch_async, method='get', url='https://www.python.org/', req_kwargs={}), gevent.spawn(fetch_async, method='get', url='https://www.yahoo.com/', req_kwargs={}), gevent.spawn(fetch_async, method='get', url='https://github.com/', req_kwargs={}), ]) # ##### 发送请求（协程池控制最大协程数量） ##### # from gevent.pool import Pool # pool = Pool(None) # gevent.joinall([ # pool.spawn(fetch_async, method='get', url='https://www.python.org/', req_kwargs={}), # pool.spawn(fetch_async, method='get', url='https://www.yahoo.com/', req_kwargs={}), # pool.spawn(fetch_async, method='get', url='https://www.github.com/', req_kwargs={}), # ])
import grequests request_list = [ grequests.get('http://httpbin.org/delay/1', timeout=0.001), grequests.get('http://fakedomain/'), grequests.get('http://httpbin.org/status/500') ] # ##### 执行并获取响应列表 ##### # response_list = grequests.map(request_list) # print(response_list) # ##### 执行并获取响应列表（处理异常） ##### # def exception_handler(request, exception): # print(request,exception) # print("Request failed") # response_list = grequests.map(request_list, exception_handler=exception_handler) # print(response_list)
from twisted.web.client import getPage, defer from twisted.internet import reactor def all_done(arg): reactor.stop() def callback(contents): print(contents) deferred_list = [] url_list = ['http://www.bing.com', 'http://www.baidu.com', ] for url in url_list: deferred = getPage(bytes(url, encoding='utf8')) deferred.addCallback(callback) deferred_list.append(deferred) dlist = defer.DeferredList(deferred_list) dlist.addBoth(all_done) reactor.run()
from tornado.httpclient import AsyncHTTPClient from tornado.httpclient import HTTPRequest from tornado import ioloop def handle_response(response): """ 处理返回值内容（需要维护计数器，来停止IO循环），调用 ioloop.IOLoop.current().stop() :param response: :return: """ if response.error: print("Error:", response.error) else: print(response.body) def func(): url_list = [ 'http://www.baidu.com', 'http://www.bing.com', ] for url in url_list: print(url) http_client = AsyncHTTPClient() http_client.fetch(HTTPRequest(url), handle_response) ioloop.IOLoop.current().add_callback(func) ioloop.IOLoop.current().start()
from twisted.internet import reactor from twisted.web.client import getPage import urllib.parse def one_done(arg): print(arg) reactor.stop() post_data = urllib.parse.urlencode({'check_data': 'adf'}) post_data = bytes(post_data, encoding='utf8') headers = {b'Content-Type': b'application/x-www-form-urlencoded'} response = getPage(bytes('http://dig.chouti.com/login', encoding='utf8'), method=bytes('POST', encoding='utf8'), postdata=post_data, cookies={}, headers=headers) response.addBoth(one_done) reactor.run()
import select import socket class WrapSpider(object): '''包装sock对象''' def __init__(self,sock,web_info): self.sock=sock self.web_info=web_info def fileno(self): return self.sock.fileno() #####容易忘记 class GreatIO(object): def __init__(self): self.coons=[] self.sock_list=[] def add_spider(self,web_info): '''添加相关请求''' sock=socket.socket() sock.setblocking(False) try: sock.connect((web_info['host'],web_info['port'])) except BlockingIOError as e: pass obj=WrapSpider(sock,web_info) self.sock_list.append(obj) self.coons.append(obj) def run(self): """ 执行请求 :return: """ while True: #select.select([对象]) #可以是任意对象，但是对象要有fileno方法 #现在对其对象进行包装，obj 是WrapSpider对象 r, w, e = select.select(self.sock_list,self.coons, [], 0.05) for obj in w: #连接成功的 data='GET %s HTTP/1.1\r\nhost:%s\r\n\r\n'.format(obj.web_info['path'],obj.web_info['host']).encode('utf-8') obj.sock.send(data) self.coons.remove(obj) for obj in r: response=obj.sock.recv(8096) obj.web_info['callback'](obj.web_info['host'],response) self.sock_list.remove(obj) if not self.sock_list: break def done(host,callbac): print(host,callbac) Spider_list=[ {'host':'www.baidu.com', 'port':80, 'path':'/index.php?tn=06074089_9_pg', 'callback':done}, {'host':'www.dig.chouti.com', 'port': 80,'path': '/','callback':done}, {'host':'www.bing.com','port':80, 'path':'/', 'callback':done}, ] qing=GreatIO() for sp in Spider_list: qing.add_spider(sp) qing.run()