模型中的 Django 过滤器

Question

我正在尝试使用 HighCharts 设置我的 django 管理页面，以便管理员可以轻松地可视化一些数据。

我目前可以获取 PeopleCount 模型中所有对象的乘客总数 (totalPeople)，但是当我尝试按 StopID (totalPeopleByStop) 进行过滤时，它会中断。

这是我的 models.py，以及 PeopleCount 类中的上述方法：

from django.db import models
from django.template.loader import render_to_string

class Vehicle(models.Model):
    VehID = models.AutoField(primary_key=True)
    Title = models.CharField(max_length=40)
    Driver = models.CharField(max_length=25)

def __unicode__(self):
    return self.Title


class Location(models.Model):
    LocID = models.AutoField(primary_key=True)
    VehID = models.ForeignKey('Vehicle')
    Latitude = models.DecimalField(max_digits=10, decimal_places=6)
    Longitude = models.DecimalField(max_digits=10, decimal_places=6)
    Speed = models.DecimalField(max_digits=4, decimal_places=1)

    def __unicode__(self):
       #VehID + LocID Identifier
       return str(self.LocID)


class PeopleCount(models.Model):
    CountID = models.AutoField(primary_key=True)
    StopID = models.ForeignKey('StopLocation')
    VehID = models.ForeignKey('Vehicle')
    LocID = models.ForeignKey('Location')
    Date = models.DateField(auto_now_add=True, blank=False)
    Time = models.TimeField(auto_now_add=True)
    Count = models.IntegerField()

    Date.editable = True
    Time.editable = True

    def totalPeople(self):
        totPeople = 0
        for model in PeopleCount.objects.all():
            totPeople += model.Count
        return totPeople

    def totalPeopleByStop(self, stopname):
        totPeople = 0
        name = stopname
        for model in PeopleCount.objects.filter(StopID=stopname).all():
            totPeople += model.Count
        return totPeople

    def __unicode__(self):
        return str(self.CountID)

    def peoplecount_chart(self):
       totalPeople = self.totalPeople()
       totalRamsey = self.totalPeopleByStop("Ramsey")
       lu = { 'categories' : [self.StopID],\
           'tot_riders' : [self.Count],\
           'tot_riders_at_stop' : [totalPeople]}

       return render_to_string('admin/tracker/peoplecount/peoplecount_chart.html', lu )
     peoplecount_chart.allow_tags = True

class StopLocation(models.Model):
    StopID = models.AutoField(primary_key=True)
    StopName = models.CharField(max_length=40)
    Latitude = models.DecimalField(max_digits=10, decimal_places=6)
    Longitude = models.DecimalField(max_digits=10, decimal_places=6)

    def __unicode__(self):
        #VehID + LocID Identifier
        return str(self.StopName)

没有任何错误通过 django 或任何日志发生，所以我不完全确定如何让 totalPeopleByStop() 正常工作。

Answer 1

您可以使用django aggregates 更轻松地完成此操作。

from django.db.models import Sum


class PeopleCount(models.Model):
   ...

   def totalPeopleByStop(self, stopname):
        return PeopleCount.objects.filter(StopID=stopname).aggregate(
            total_people_by_stop=Sum('Count'))['total_people_by_stop']