class MiddlewareMixin(object):
  def __init__(self, get_response=None):
    self.get_response = get_response
    super(MiddlewareMixin, self).__init__()

  def __call__(self, request):
    response = None
    if hasattr(self, 'process_request'):
      response = self.process_request(request)
    if not response:
      response = self.get_response(request)
    if hasattr(self, 'process_response'):
      response = self.process_response(request, response)
    return response

class My_middleware(MiddlewareMixin):
  def __init__(self,get_response=None):
    super().__init__(get_response)

  def process_request(self,request):
    """
    视图函数前执行的，一旦这里有return将到达不了视图函数
    request是浏览器发过来的请求
    """
    print("视图函数执行前")

  def process_response(self,request,response):
    """
    视图函数后执行的
    request是浏览器发过来的请求
    response是视图函数返回的响应
    """
    print("视图函数执行后")

    # 因为你拿了视图函数的response，就算处理的业务与response无关也要返回response
    return response

MIDDLEWARE = [
  ...
  'middlewares.My_middleware'  # 写上自己的路径
]

before 视图（中间件1）
before 视图 2（中间件2）
==index==
after 视图 2（中间件2）
after 视图（中间件1）