Django 按小时/天分组 [英] Django group by hour/day

问题描述

我有一个模型:

模型.py

class DispatchPlan(models.Model):
    total_trucks = models.IntegerField(default=0)
    material_type = models.CharField(max_length=255, default=0, choices=mtypes)
    scheduled_date = models.DateTimeField(max_length=255, default=0)
    offered_price = models.IntegerField(default=0)
    weight = models.IntegerField(default=0)

我正在尝试在 schedule_date 和 weight 之间绘制图表.我想相应地按小时和重量对时间戳进行分组.我该怎么做?

and I am trying to plot a graph between scheduled_date and weight. I want to group the timestamp by hour and weight accordingly. How can I do that?

在 SQl 中它就像 .groupby('scheduled_date) 但由于它是一个时间戳，我认为它不一样

In SQl its just like .groupby('scheduled_date) but since it's a timestamp, I don't think it's the same

应该是这样的:

data = DispatchPlan.objects.all().groupby('scheduled_date')

我使用 postgres 作为我的数据库.

I am using postgres as my database.

我试过的

dataset = DispatchPlan.objects.annotate(month=TruncMonth('scheduled_date')).values('month').annotate(c=sum('weight')).values('month', 'c')

错误:

TypeError: 不支持 + 的操作数类型:'int' 和 'str'

TypeError: unsupported operand type(s) for +: 'int' and 'str'

推荐答案

您需要使用 Django 的 Sum 方法，而不是 Python 的 sum.所以做这样的事情:

You need to use Django's Sum method instead of Python's sum. So do something like this:

from django.db.models import Sum

dataset = DispatchPlan.objects.annotate(month=TruncMonth('scheduled_date')).values('month').annotate(c=Sum('weight')).values('month', 'c')

因为您似乎想按小时分组，所以您应该使用 TrncHour 代替:

As it seems you want to group by hour you should be using TruncHour instead:

from django.db.models import Sum
from django.db.models.functions import TruncHour

dataset = DispatchPlan.objects.annotate( 
    hour=TruncHour('scheduled_date')
).values(
    'hour'
).annotate(
    c=Sum('weight')
).values(
    'hour', 
    'c',
)

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