反爬（使用middleware中间件来限制IP频率）

中间件middleware里：

import time
from django.utils.deprecation import MiddlewareMixin
MAX_REQUEST_PER_SECOND=2 #每秒访问次数

class RequestBlockingMiddleware(MiddlewareMixin):
    def process_request(self,request):
        now=time.time()
        request_queue = request.session.get('request_queue',[])
        if len(request_queue) < MAX_REQUEST_PER_SECOND:
            request_queue.append(now)
            request.session['request_queue']=request_queue
        else:
            time0=request_queue[0]
            if (now-time0)<1:
                time.sleep(5)
            request_queue.append(time.time())
            request.session['request_queue']=request_queue[1:]

#启用RequestBlocking中间件
IDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'app.middleware.RequestBlockingMiddleware', #在sessions之后，auth之前
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]