Django查询如何对返回的对象求和方法
我有一个模型:Django查询如何对返回的对象求和方法,django,Django,我有一个模型: class TimeStamp(models.Model): user = models.ForeignKey(User, on_delete=models.CASCADE) t_in = models.DateTimeField(_("In"), auto_now=False, auto_now_add=False) t_out = models.DateTimeField( _("Out"), a
class TimeStamp(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
t_in = models.DateTimeField(_("In"), auto_now=False, auto_now_add=False)
t_out = models.DateTimeField(
_("Out"), auto_now=False, auto_now_add=False, blank=True, null=True)
class Meta:
verbose_name = _("TimeStamp")
verbose_name_plural = _("TimeStamps")
def __str__(self):
return str(f'{self.t_in.date()} {self.user.get_full_name()}')
def get_absolute_url(self):
return reverse("TimeStamp_detail", kwargs={"pk": self.pk})
def get_total_hrs(self):
if self.t_out:
t_hrs = abs(self.t_out-self.t_in).total_seconds()/3600
else:
t_hrs = '0'
return str(t_hrs)
然后在我的观点里
def timeclock_view(request):
week_start = timezone.now().date()
week_start -= timedelta(days=(week_start.weekday()+1) % 7)
week_end = week_start + timedelta(days=7)
obj = request.user.timestamp_set.filter(
t_in__gte=week_start, t_in__lt=week_end)
obj.aggregate(total_hrs=Sum('get_total_hrs'))
if obj:
last = obj.last()
context = {'obj': obj, 'last': last,
'week_start': week_start, 'week_end': week_end, 'week_total': total_hrs, }
else:
context = {}
return render(request, 'timeclock/timeclock_view.html', context)
我如何写这个来获得查询集的小时数?
obj.aggregate(total_hrs=Sum('get_total_hrs))
给了我一个错误:
django.core.exceptions.FieldError:无法解析关键字
将“总小时数”输入字段。选项包括:描述、id、注释、,
注意设置,密码,输入,输出,用户,用户id
聚合是在数据库上完成的。这意味着您只能使用聚合中的字段,而不能使用模型函数或属性 我将首先使用
annotate()
queryset实现get\u total\u hrs
的逻辑,然后使用this queryset在计算字段上进行聚合
from django.db.models.functions import Abs
from django.db.models import F, ExpressionWrapper, DurationField, Sum
queryset.annotate(
total_hrs=ExpressionWrapper(
Abs(F("t_out") - F("t_in")),
output_field=DurationField()
),
).aggregate(overall_hrs=Sum("total_hrs"))
只能聚合字段<代码>获取总小时数是一种方法。