Python 如何使用ForeignKey对字段求和？

专家与choosen员工填写空白列表
5名专家，将有5份空白名单。如何计算五张空白清单的总和

型号.py：

ANSWER_TYPES = (
    (0, 0),
    (1, 1),
    )

class Expert(models.Model):
    expertname = models.CharField(max_length=200, null=True)
    position = models.CharField(max_length=200, null=True)

class Employee(models.Model):
    employeename = models.CharField(max_length=200, null=True)
    position = models.CharField(max_length=200, null=True)

class Blank_list(models.Model):
    expert_name = models.ForeignKey(Expert, null=True, on_delete=models.SET_NULL)
    employee_name = models.ForeignKey(Employee, null=True, on_delete=models.SET_NULL)
    lvl_1 = models.IntegerField('Indicator1:1', choices=ANSWER_TYPES, blank=0)
    lvl_2 = models.IntegerField('Indicator1:2', choices=ANSWER_TYPES, blank=0)
    lvl_3 = models.IntegerField('Indicator1:3', choices=ANSWER_TYPES, blank=0)

class EmployeeCard(models.Model):
    blank_list = models.ManyToManyField(Blank_list, null=True, ) #there is a list of Blank_list
    #don't know if blank_list a correct field?
    employee_name = models.ForeignKey(Employee, null=True, on_delete=models.SET_NULL)
    sum_of_all_blank_list = ...

然后，您可以使用空白列表计数作为员工视图上的字段

然后，您可以使用空白列表计数作为员工视图上的字段

class Employee(models.Model):
    employeename = models.CharField(max_length=200, null=True)
    position = models.CharField(max_length=200, null=True)

    def blank_list_count(self):
        return Blank_list.objects.filter(employeename = self).count()