python - 如何在 Django 中对模型的所有实例求和

Question

这些是我的模型

class Countries(models.Model):
    Name = models.CharField(max_length=100)
    Language = models.IntegerField()
    Population = models.IntegerField(default=0)

class World(models.Model):
    Languages_spoken = model.Charfield(max_length=12000)
    World_population = models.IntegerField(default=0)

我正在尝试添加Population Countries 中的所有实例总结并显示在 World_population类里面的田野World

我尝试过的

class World(models.Model):
    Languages_spoken = model.Charfield(max_length=12000)
    World_population = models.IntegerField(default=0)
    def save(self, *args, **kwargs):
        self.World_population = Countries.objects.get(Population) # I know this is not correct
        super(World,self).save()

Answer 1

试一下:

from django.db.models import Sum
Countries.objects.aggregate(total_population=Sum('Population'))

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