如何使用列表理解对计算的模型值进行过滤 [英] How to filter on calculated model values using list comprehension

问题描述

我有一个用于计算总计的模型

I have a model where I calculate totals

class Material(models.Model):
    version = IntegerVersionField( )
    code = models.CharField(max_length=30)
    name = models.CharField(max_length=30)
    slug = models.SlugField(max_length=80, blank=True)
    description = models.TextField(null=True, blank=True)
    min_quantity = models.DecimalField(max_digits=19, decimal_places=10)

    def _get_totalinventory(self):
        from inventory.models import Inventory
        return Inventory.objects.filter(warehouse_Bin__material_UOM__UOM__material=self.id, is_active = True).aggregate(Sum('quantity'))

    total_inventory = property(_get_totalinventory)

    def _get_totalpo(self):
        from purchase.models import POmaterial     
        return POmaterial.objects.filter(material=self.id, is_active = True).aggregate(Sum('quantity'))  

    total_po = property(_get_totalpo)


    def _get_totalso(self):
        from sales.models import SOproduct
        return SOproduct.objects.filter(product__material=self.id ,  is_active=True ).aggregate(Sum('quantity'))  

    total_so = property(_get_totalso)

到目前为止，我的计算字段正确计算并显示在模板中，没有任何问题

So far so good , my calculate fields calculate correctly and are displayed in template without any problem

由于我无法直接按属性过滤，因此建议使用python列表理解力

Since I can not filter directly by the property As suggested i am using python list comprehension

所以这是我写的，确实给了我输出，没有错误。

So this is what I wrote that does give me output and no errors .

    po_list = [n for n in Material.objects.all() 

if ((F('total_inventory') + F('total_po') - F('total_so')) < F('min_quantity'))]

但是当前列表理解不能正确过滤
我得到的输出应该被过滤掉。我在做什么错？

However Current list comprehension doesn't filter correctly I am getting output that should be filtered out. What i am doing wrong?

它没有过滤任何东西，只是返回了列表而已

It is not filtering anything it is just returning the list a it is

推荐答案

我怀疑您可以在模型类方法上调用 F 。相反，您可以直接从列表理解中的对象调用方法：

I doubt you can call F on model class methods. You can instead call the methods directly from the objects in the list comprehension:

po_list = [n for n in Material.objects.all() if (n.total_inventory['quantity__sum'] 
                                                 + n.total_po['quantity__sum'] 
                                                 - n.total_so['quantity__sum']) 
                                                 < n.min_quantity]

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