求问，django中如何计算日期差？计算某个日期距离今日之间天数

from django.db import models
import  datetime

class Customer(models.Model):

     deal_date = models.DateTimeField(auto_now_add=True,verbose_name="创建时间")
     today = datetime.datetime.now().date()

class MyClassViewSet(viewsets.ModelViewSet):
    serializer_class = MyClassSerializer
    permission_classes = (IsAuthenticated, )

    def perform_create(self, serializer):
        if (condition):
            start_date = datetime.datetime.strptime(self.request.data.get('dateDeFin'), "%Y-%m-%d %H:%M")
            end_date = datetime.datetime.strptime(self.request.data.get('dateDeDebut'), "%Y-%m-%d %H:%M")
            diff = abs((end_date-start_date).days)
        print(diff)