request.COOKIES.has_key('<cookie_name>')

request.COOKIES.get('visits', '1')
if 'last_visit' in request.COOKIES:
 request.COOKIES['last_visit']

response.set_cookie('<cookie_name>', value)

fav_color = request.session.get('fav_color', 'red')
fav_color = request.session['fav_color']

request.session['visits'] = visits

del request.session['fav_color']

'fav_color' in request.session

python manage.py clearsessions

#注册
def regist(req):
  if req.method == 'POST':
    uf = UserForm(req.POST)
    if uf.is_valid():
      #获得表单数据
      username = uf.cleaned_data['username']
      password = uf.cleaned_data['password']
      #添加到数据库
      User.objects.create(username= username,password=password)
      return HttpResponse('regist success!!')
  else:
    uf = UserForm()
  return render_to_response('regist.html',{'uf':uf}, context_instance=RequestContext(req))
#登陆
def login(req):
  if req.method == 'POST':
    uf = UserForm(req.POST)
    if uf.is_valid():
      #获取表单用户密码
      username = uf.cleaned_data['username']
      password = uf.cleaned_data['password']
      #获取的表单数据与数据库进行比较
      user = User.objects.filter(username__exact = username,password__exact = password)
      if user:
        #比较成功，跳转index
        response = HttpResponseRedirect('/online/index/')
        #将username写入浏览器cookie,失效时间为3600
        response.set_cookie('username',username,3600)
        return response
      else:
        #比较失败，还在login
        return HttpResponseRedirect('/online/login/')
  else:
    uf = UserForm()
  return render_to_response('login.html',{'uf':uf},context_instance=RequestContext(req))
#登陆成功
def index(req):
  username = req.COOKIES.get('username','')
  return render_to_response('index.html' ,{'username':username})
#退出
def logout(req):
  response = HttpResponse('logout !!')
  #清理cookie里保存username
  response.delete_cookie('username')
  return response