【小沐学Python】Python实现Web服务器（aiohttp）

1、简介

https://github.com/aio-libs/aiohttp
https://docs.aiohttp.org/en/stable/index.html

Asynchronous HTTP client/server framework for asyncio and Python
异步 http 客户端/服务器框架

主要特点:

• 支持 HTTP 协议的客户端和服务器端。
• 支持开箱即用的客户端和服务器 Web 套接字，并避免 回调地狱。
• 为 Web 服务器提供中间件和可插拔路由。

2、下载和安装

安装库：

pip3 install aiohttp
# pip install aiodns
# pip install aiohttp[speedups]

3、代码测试

3.1 客户端

• 客户端：要从网络上获取某些内容。

import aiohttp
import asyncio

async def main():

    async with aiohttp.ClientSession() as session:
        async with session.get('https://www.baidu.com/') as response:

            print("Status:", response.status)
            print("Content-type:", response.headers['content-type'])

            html = await response.text()
            print("Body:", html[:15], "...")

asyncio.run(main())

运行之后：

报错了。
修改代码如下：

import aiohttp
import asyncio

async def main():

    async with aiohttp.ClientSession() as session:
        async with session.get('https://www.baidu.com/') as response:

            print("Status:", response.status)
            print("Content-type:", response.headers['content-type'])

            html = await response.text()
            print("Body:", html[:15], "...")

# asyncio.run(main())
loop = asyncio.get_event_loop()
loop.run_until_complete(main())

再次运行之后，没有报错。

3.2 服务端

• 服务器：使用简单服务器的示例。

# examples/server_simple.py
from aiohttp import web

async def handle(request):
    name = request.match_info.get('name', "Anonymous")
    text = "Hello, " + name
    return web.Response(text=text)

async def wshandle(request):
    ws = web.WebSocketResponse()
    await ws.prepare(request)

    async for msg in ws:
        if msg.type == web.WSMsgType.text:
            await ws.send_str("Hello, {}".format(msg.data))
        elif msg.type == web.WSMsgType.binary:
            await ws.send_bytes(msg.data)
        elif msg.type == web.WSMsgType.close:
            break

    return ws


app = web.Application()
app.add_routes([web.get('/', handle),
                web.get('/echo', wshandle),
                web.get('/{name}', handle)])

if __name__ == '__main__':
    web.run_app(app)

运行之后：

浏览器访问网址：

http://127.0.0.1:8080/

4、更多测试

4.1 asyncio

asyncio是Python 3.4版本引入的标准库，直接内置了对异步IO的支持。

asyncio的编程模型就是一个消息循环。我们从asyncio模块中直接获取一个EventLoop的引用，然后把需要执行的协程扔到EventLoop中执行，就实现了异步IO。

import asyncio

@asyncio.coroutine
def hello():
    print("Hello world!111")
    print("Hello world!22")
    # 异步调用asyncio.sleep(1):
    r = yield from asyncio.sleep(1)
    print("Hello again!333")
    print("Hello again!444")

# 获取EventLoop:
loop = asyncio.get_event_loop()
# 执行coroutine
loop.run_until_complete(hello())
loop.close()

import threading
import asyncio

@asyncio.coroutine
def hello():
    print('Hello world! (%s)' % threading.currentThread())
    yield from asyncio.sleep(1)
    print('Hello again! (%s)' % threading.currentThread())

loop = asyncio.get_event_loop()
tasks = [hello(), hello()]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()

import asyncio

@asyncio.coroutine
def wget(host):
    print('wget %s...' % host)
    connect = asyncio.open_connection(host, 80)
    reader, writer = yield from connect
    header = 'GET / HTTP/1.0\r\nHost: %s\r\n\r\n' % host
    writer.write(header.encode('utf-8'))
    yield from writer.drain()
    while True:
        line = yield from reader.readline()
        if line == b'\r\n':
            break
        print('%s header > %s' % (host, line.decode('utf-8').rstrip()))
    # Ignore the body, close the socket
    writer.close()

loop = asyncio.get_event_loop()
tasks = [wget(host) for host in ['www.sina.com.cn', 'www.sohu.com', 'www.163.com']]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()

asyncio提供了完善的异步IO支持；
异步操作需要在coroutine中通过yield from完成；

4.2 aiohttp+HTTP服务器

编写一个HTTP服务器:

import asyncio

from aiohttp import web

async def index(request):
    await asyncio.sleep(0.5)
    return web.Response(text='<h1>Index</h1>', content_type= 'text/html')

async def hello(request):
    await asyncio.sleep(0.5)
    text = '<h1>hello, %s!</h1>' % request.match_info['name']
    return web.Response(text=text, content_type= 'text/html')

async def init(loop):
    app = web.Application(loop=loop)
    app.router.add_route('GET', '/', index)
    app.router.add_route('GET', '/hello/{name}', hello)
    srv = await loop.create_server(app.make_handler(), '127.0.0.1', 8000)
    print('Server started at http://127.0.0.1:8000...')
    return srv

loop = asyncio.get_event_loop()
loop.run_until_complete(init(loop))
loop.run_forever()

4.3 aiohttp+爬虫实例

pip install bs4 

编写一个爬虫实例:

import asyncio
import aiohttp
from bs4 import BeautifulSoup
import logging

class AsnycSpider(object):

    def __init__(self, url_list, max_threads):

        self.urls = url_list
        self.results = {}
        self.max_threads = max_threads

    def __parse_results(self, url, html):
        try:
            soup = BeautifulSoup(html, 'html.parser')
            title = soup.find('title').get_text()
        except Exception as e:
            raise e

        if title:
            self.results[url] = title

    async def get_body(self, url):
        async with aiohttp.ClientSession() as session:
            async with session.get(url, timeout=30) as response:
                assert response.status == 200
                html = await response.read()
                return response.url, html

    async def get_results(self, url):
        url, html = await self.get_body(url)
        self.__parse_results(url, html)
        return 'Completed'

    async def handle_tasks(self, task_id, work_queue):
        while not work_queue.empty():
            current_url = await work_queue.get()
            try:
                task_status = await self.get_results(current_url)
            except Exception as e:
                logging.exception('Error for {}'.format(current_url), exc_info=True)

    def eventloop(self):
        q = asyncio.Queue()
        [q.put_nowait(url) for url in self.urls]
        loop = asyncio.get_event_loop()
        tasks = [self.handle_tasks(task_id, q, ) for task_id in range(self.max_threads)]
        loop.run_until_complete(asyncio.wait(tasks))
        # loop.close()

if __name__ == '__main__':
    async_example = AsnycSpider([
        'https://www.qq.com/',
        'https://www.163.com/',
        'https://news.baidu.com/',
        'https://blog.csdn.net/'], 5)
    async_example.eventloop()
    print(async_example.results)

4.4 aiohttp+requests比较

在 Python 众多的 HTTP 客户端中，有这几个：requests、aiohttp和httpx。在不借助其他第三方库的情况下，requests只能发送同步请求；aiohttp只能发送异步请求；httpx既能发送同步请求，又能发送异步请求。

pip install requests

• test_requests.py

import random
import time
import datetime
import requests


def make_request(session):
    resp = session.get('http://httpbin.org/get')
    # result = resp.text
    # print(result)
    pass


def main():
    session = requests.Session()
    start = time.time()
    for _ in range(100):
        make_request(session)
    end = time.time()
    print(f'发送100次请求，耗时：{end - start}')


if __name__ == '__main__':
    main()

• test_aiohttp.py

import aiohttp
import random
import datetime
import asyncio
import time

async def request(client):
    async with client.get('http://httpbin.org/get') as resp:
        # print(resp.status)
        # print(await resp.text())
        pass

async def main():
    async with aiohttp.ClientSession() as client:
        start = time.time()
        task_list = []
        for _ in range(100):
            req = request(client)
            task = asyncio.create_task(req)
            task_list.append(task)
        await asyncio.gather(*task_list)
        end = time.time()
    print(f'发送100次请求，耗时：{end - start}')

asyncio.run(main())

结语

如果您觉得该方法或代码有一点点用处，可以给作者点个赞，或打赏杯咖啡；╮(￣▽￣)╭
如果您感觉方法或代码不咋地//(ㄒoㄒ)//，就在评论处留言，作者继续改进；o_O???
如果您需要相关功能的代码定制化开发，可以留言私信作者；(????)
感谢各位大佬童鞋们的支持！( ′ ▽′ )ﾉ ( ′ ▽′)っ！！！