小编Lak*_*har的帖子

我必须在 django 模板中减去两个值。我怎样才能做到这一点 ？

{{ obj.loan_amount }} - {{ obj.service_charge }}

我想过滤我的查询集,当且仅当loan我的模型中存在ShgGroupLoanMarking.

class ShgGroupLoanMarking(models.Model):
 shg = models.ForeignKey(Shg, null=True)
 category = models.CharField(max_length=25, choices=GROUP_CATEGORY, default="shg_group")
 msss = models.ForeignKey(Msss, null=True)
 shgmember = models.ForeignKey(ShgMember, null=True)
 loan = models.ForeignKey(Loan, null=True)
 date_of_marking = models.DateField(null=True)
 paid = models.CharField(max_length=100, null=True)
 loan_amount = models.CharField(max_length=100, null=True)
 service_charge = models.CharField(max_length=100, null=True)
 description = models.CharField(max_length=100, null=True)
 status = models.CharField(max_length=100, null=True)
 print_status = models.BooleanField(default=False)
 sent_to_bank_status = models.BooleanField(default=False)
 receipt_number = models.IntegerField(default=0)

这该怎么做？