目录
高性能的异步爬虫
一. 同步爬取
1. 普通爬取
# 普通爬取
from time import sleep
import time
from multiprocessing.dummy import Pool
def request(url):
print('正在下载:', url)
sleep(2)
print('下载成功:', url)
start = time.time()
urls = [
'www.baidu.com',
'www.taobao.com',
'www.sogou.com'
]
for url in urls:
request(url)
print('总耗时:', time.time()-start)
正在下载: www.baidu.com
下载成功: www.baidu.com
正在下载: www.taobao.com
下载成功: www.taobao.com
正在下载: www.sogou.com
下载成功: www.sogou.com
总耗时: 6.003343343734741
2. 线程池爬取
# 使用线程池
from time import sleep
import time
from multiprocessing.dummy import Pool
def request(url):
print('正在下载:', url)
sleep(2)
print('下载成功:', url)
start = time.time()
urls = [
'www.baidu.com',
'www.taobao.com',
'www.sogou.com'
]
pool = Pool(3)
pool.map(request, urls)
print('总耗时', time.time()-start)
二. 异步asyncio基本使用
1. 基本使用
# 基本使用
import asyncio
async def hello(name):
print('hello to:', name)
# 获取一个协程对象
c = hello('konghui')
# 创建一个事件循环对象
loop = asyncio.get_event_loop()
# 将协程对象注册到事件循环中, 然后启动事件循环
loop.run_until_complete(c)
hello to: konghui
2. task的使用
# task的使用
import asyncio
async def hello(name):
print('hello to:', name)
c = hello('konghui')
loop = asyncio.get_event_loop()
# 就协程进行进一步的封装, 封装到了task对象中
task = loop.create_task(c)
print(task)
loop.run_until_complete(task)
print(task)
<Task pending coro=<hello() running at <ipython-input-11-91468b72d8d0>:5>>
hello to: konghui
<Task finished coro=<hello() done, defined at <ipython-input-11-91468b72d8d0>:5> result=None>
3. future的使用
# future的使用
import asyncio
async def hello(name):
print('hello to:', name)
c = hello('konghui')
future = asyncio.ensure_future(c)
loop.run_until_complete(future)
hello to: konghui
4. 绑定回调
# 绑定回调(task)
def callback(task):
print('i am callback', task.result())
import asyncio
async def hello(name):
print('hello to:', name)
return name
c = hello('konghui')
task = asyncio.ensure_future(c)
# 给任务对象绑定一个回调函数
task.add_done_callback(callback)
loop.run_until_complete(task)
hello to: konghui
i am callback konghui
'konghui'
二. 异步asyncio案例对比
案例一:
import asyncio
async def request(url):
print('正在下载：',url)
sleep(2) #非异步模块的代码：在此处如果存在非异步操作代码，则会彻底让asyncio失去异步的效果
print('下载成功：',url)
urls = [
'www.baidu.com',
'www.taobao.com',
'www.sogou.com'
]
start = time.time()
loop = asyncio.get_event_loop()
tasks = [] #任务列表，放置多个任务对象
for url in urls:
c = request(url)
task = asyncio.ensure_future(c)
tasks.append(task)
#将多个任务对象对应的列表注册到事件循环中
loop.run_until_complete(asyncio.wait(tasks))
print('总耗时：',time.time()-start)
正在下载： www.baidu.com
下载成功： www.baidu.com
正在下载： www.taobao.com
下载成功： www.taobao.com
正在下载： www.sogou.com
下载成功： www.sogou.com
总耗时： 6.006343603134155
案例二:
import asyncio
async def request(url):
print('正在下载：',url)
# sleep(2) #非异步模块的代码：在此处如果存在非异步操作代码，则会彻底让asyncio失去异步的效果
await asyncio.sleep(2)
print('下载成功：',url)
urls = [
'www.baidu.com',
'www.taobao.com',
'www.sogou.com'
]
start = time.time()
loop = asyncio.get_event_loop()
tasks = [] #任务列表，放置多个任务对象
for url in urls:
c = request(url)
task = asyncio.ensure_future(c)
tasks.append(task)
#将多个任务对象对应的列表注册到事件循环中
loop.run_until_complete(asyncio.wait(tasks))
print('总耗时：',time.time()-start)
正在下载： www.baidu.com
正在下载： www.taobao.com
正在下载： www.sogou.com
下载成功： www.baidu.com
下载成功： www.taobao.com
下载成功： www.sogou.com
总耗时： 2.0051145553588867
案例三:
import aiohttp
import asyncio
async def get_page(url):
async with aiohttp.ClientSession() as session:
async with await session.get(url=url) as response:
page_text = await response.text() #read() json()
print(page_text)
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',
'http://127.0.0.1:5000/bobo',
'http://127.0.0.1:5000/jay',
'http://127.0.0.1:5000/tom',
'http://127.0.0.1:5000/bobo',
'http://127.0.0.1:5000/jay',
'http://127.0.0.1:5000/tom'
]
tasks = []
loop = asyncio.get_event_loop()
for url in urls:
c = get_page(url)
task = asyncio.ensure_future(c)
tasks.append(task)
loop.run_until_complete(asyncio.wait(tasks))
print('总耗时：',time.time()-start)
Hello bobo
Hello jay
Hello tom
Hello jay
Hello bobo
Hello tom
Hello bobo
Hello tom
Hello jay
总耗时： 2.031116008758545