老男孩IT教育Python培训教你如何使用python web框架

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Python的Web框架中Tornado以异步非阻塞而闻名。本篇将使用200行代码完成一个微型异步非阻塞Web框架：Snow。

一、源码

本文基于非阻塞的Socket以及IO多路复用从而实现异步非阻塞的Web框架，其中便是众多异步非阻塞Web框架内部原理。

#!/usr/bin/env python# -*- coding:utf-8 -*-import reimport socketimport selectimport timeclass HttpResponse(object):   """
   封装响应信息   """
    def __init__(self, content=''):
     self.content = content

     self.headers = {}
     self.cookies = {}   def response(self):     return bytes(self.content, encoding='utf-8')class HttpNotFound(HttpResponse):   """
   404时的错误提示   """
    def __init__(self):
     super(HttpNotFound, self).__init__('404 Not Found')class HttpRequest(object):   """
   用户封装用户请求信息   """
    def __init__(self, conn):
     self.conn = conn

     self.header_bytes = bytes()
     self.header_dict = {}
     self.body_bytes = bytes()

     self.method = ""
     self.url = ""
     self.protocol = ""

     self.initialize()
     self.initialize_headers()   def initialize(self):

     header_flag = False     while True:       try:
         received = self.conn.recv(8096)       except Exception as e:
         received = None       if not received:         break
            if header_flag:
         self.body_bytes += received         continue
       temp = received.split(b'\r\n\r\n', 1)       if len(temp) == 1:
         self.header_bytes += temp       else:
         h, b = temp
         self.header_bytes += h
         self.body_bytes += b
         header_flag = True

   @property   def header_str(self):     return str(self.header_bytes, encoding='utf-8')   def initialize_headers(self):
     headers = self.header_str.split('\r\n')
     first_line = headers[0].split(' ')     if len(first_line) == 3:
       self.method, self.url, self.protocol = headers[0].split(' ')       for line in headers:
         kv = line.split(':')         if len(kv) == 2:
           k, v = kv
           self.header_dict[k] = vclass Future(object):   """
   异步非阻塞模式时封装回调函数以及是否准备就绪   """
    def __init__(self, callback):
     self.callback = callback
     self._ready = False
     self.value = None   def set_result(self, value=None):
     self.value = value
     self._ready = True

   @property   def ready(self):     return self._readyclass TimeoutFuture(Future):   """
   异步非阻塞超时   """
    def __init__(self, timeout):
     super(TimeoutFuture, self).__init__(callback=None)
     self.timeout = timeout
     self.start_time = time.time()

   @property   def ready(self):
     current_time = time.time()     if current_time > self.start_time + self.timeout:
       self._ready = True     return self._readyclass Snow(object):   """
   微型Web框架类   """
    def __init__(self, routes):
     self.routes = routes
     self.inputs = set()
     self.request = None
     self.async_request_handler = {}   def run(self, host='localhost', port=9999):     """
     事件循环
     :param host:
     :param port:
     :return:     """
     sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     sock.bind((host, port,))
     sock.setblocking(False)
     sock.listen(128)
     sock.setblocking(0)
     self.inputs.add(sock)     try:       while True:
         readable_list, writeable_list, error_list = select.select(self.inputs, [], self.inputs,0.005)         for conn in readable_list:           if sock == conn:
             client, address = conn.accept()
             client.setblocking(False)
             self.inputs.add(client)           else:
             gen = self.process(conn)             if isinstance(gen, HttpResponse):
               conn.sendall(gen.response())
               self.inputs.remove(conn)
               conn.close()             else:
               yielded = next(gen)
               self.async_request_handler[conn] = yielded
         self.polling_callback()     except Exception as e:       pass
        finally:
       sock.close()   def polling_callback(self):     """
     遍历触发异步非阻塞的回调函数
     :return:     """
        for conn in list(self.async_request_handler.keys()):
       yielded = self.async_request_handler[conn]       if not yielded.ready:         continue
            if yielded.callback:
         ret = yielded.callback(self.request, yielded)
         conn.sendall(ret.response())
       self.inputs.remove(conn)       del self.async_request_handler[conn]
       conn.close()   def process(self, conn):     """
     处理路由系统以及执行函数
     :param conn:
     :return:     """
     self.request = HttpRequest(conn)
     func = None     for route in self.routes:       if re.match(route[0], self.request.url):
         func = route[1]         break
        if not func:       return HttpNotFound()     else:       return func(self.request)

二、使用

1. 基本使用

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from snow import Snow from snow import HttpResponse def index(request):     return HttpResponse('OK') routes = [     (r'/index/', index), ] app = Snow(routes) app.run(port=8012)

2.异步非阻塞：超时

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from snow import Snow from snow import HttpResponse from snow import TimeoutFuture request_list = [] def async(request):     obj = TimeoutFuture(5)     yield obj def home(request):     return HttpResponse('home') routes = [     (r'/home/', home),     (r'/async/', async), ] app = Snow(routes) app.run(port=8012)

3.异步非阻塞：等待

基于等待模式可以完成自定制操作

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from snow import Snow from snow import HttpResponse from snow import Future request_list = [] def callback(request, future):     return HttpResponse(future.value) def req(request):     obj = Future(callback=callback)     request_list.append(obj)     yield obj def stop(request):     obj = request_list[0]     del request_list[0]     obj.set_result('done')     return HttpResponse('stop') routes = [     (r'/req/', req),     (r'/stop/', stop), ] app = Snow(routes) app.run(port=8012)

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