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單線程+多任務(wù)異步協(xié)程
在函數(shù)(特殊函數(shù))定義的時候,使用async修飾,函數(shù)調(diào)用后,內(nèi)部語句不會立即執(zhí)行,而是會返回一個協(xié)程對象
任務(wù)對象=高級的協(xié)程對象(進一步封裝)=特殊的函數(shù)
任務(wù)對象必須要注冊到時間循環(huán)對象中
給任務(wù)對象綁定回調(diào):爬蟲的數(shù)據(jù)解析中
當(dāng)做是一個裝載任務(wù)對象的容器
當(dāng)啟動事件循環(huán)對象的時候,存儲在內(nèi)的任務(wù)對象會異步執(zhí)行
time.sleep -- asyncio.sleep
requests -- aiohttp
import asyncio import time start_time = time.time() async def get_request(url): await asyncio.sleep(2) print(url,'下載完成!') urls = [ 'www.1.com', 'www.2.com', ] task_lst = [] # 任務(wù)對象列表 for url in urls: c = get_request(url) # 協(xié)程對象 task = asyncio.ensure_future(c) # 任務(wù)對象 # task.add_done_callback(...) # 綁定回調(diào) task_lst.append(task) loop = asyncio.get_event_loop() # 事件循環(huán)對象 loop.run_until_complete(asyncio.wait(task_lst)) # 注冊,手動掛起
線程池+requests模塊
# 線程池 import time from multiprocessing.dummy import Pool start_time = time.time() url_list = [ 'www.1.com', 'www.2.com', 'www.3.com', ] def get_request(url): print('正在下載...',url) time.sleep(2) print('下載完成!',url) pool = Pool(3) pool.map(get_request,url_list) print('總耗時:',time.time()-start_time)
兩個方法提升爬蟲效率
起一個flask服務(wù)端
from flask import Flask import time app = Flask(__name__) @app.route('/bobo') def index_bobo(): time.sleep(2) return 'hello bobo!' @app.route('/jay') def index_jay(): time.sleep(2) return 'hello jay!' @app.route('/tom') def index_tom(): time.sleep(2) return 'hello tom!' if __name__ == '__main__': app.run(threaded=True)
aiohttp模塊+單線程多任務(wù)異步協(xié)程
import asyncio import aiohttp import requests import time start = time.time() async def get_page(url): # page_text = requests.get(url=url).text # print(page_text) # return page_text async with aiohttp.ClientSession() as s: #生成一個session對象 async with await s.get(url=url) as response: page_text = await response.text() print(page_text) return page_text urls = [ 'http://127.0.0.1:5000/bobo', 'http://127.0.0.1:5000/jay', 'http://127.0.0.1:5000/tom', ] tasks = [] for url in urls: c = get_page(url) task = asyncio.ensure_future(c) tasks.append(task) loop = asyncio.get_event_loop() loop.run_until_complete(asyncio.wait(tasks)) end = time.time() print(end-start) # 異步執(zhí)行! # hello tom! # hello bobo! # hello jay! # 2.0311079025268555
''' aiohttp模塊實現(xiàn)單線程+多任務(wù)異步協(xié)程 并用xpath解析數(shù)據(jù) ''' import aiohttp import asyncio from lxml import etree import time start = time.time() # 特殊函數(shù):請求的發(fā)送和數(shù)據(jù)的捕獲 # 注意async with await關(guān)鍵字 async def get_request(url): async with aiohttp.ClientSession() as s: async with await s.get(url=url) as response: page_text = await response.text() return page_text # 返回頁面源碼 # 回調(diào)函數(shù),解析數(shù)據(jù) def parse(task): page_text = task.result() tree = etree.HTML(page_text) msg = tree.xpath('/html/body/ul//text()') print(msg) urls = [ 'http://127.0.0.1:5000/bobo', 'http://127.0.0.1:5000/jay', 'http://127.0.0.1:5000/tom', ] tasks = [] for url in urls: c = get_request(url) task = asyncio.ensure_future(c) task.add_done_callback(parse) #綁定回調(diào)函數(shù)! tasks.append(task) loop = asyncio.get_event_loop() loop.run_until_complete(asyncio.wait(tasks)) end = time.time() print(end-start)
requests模塊+線程池
import time import requests from multiprocessing.dummy import Pool start = time.time() urls = [ 'http://127.0.0.1:5000/bobo', 'http://127.0.0.1:5000/jay', 'http://127.0.0.1:5000/tom', ] def get_request(url): page_text = requests.get(url=url).text print(page_text) return page_text pool = Pool(3) pool.map(get_request, urls) end = time.time() print('總耗時:', end-start) # 實現(xiàn)異步請求 # hello jay! # hello bobo! # hello tom! # 總耗時: 2.0467123985290527
小結(jié)
aiohttp模塊+單線程多任務(wù)異步協(xié)程
requests模塊+線程池
requests
urllib
aiohttp
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