django中的乘法

Question

我如何在预算模型中将两个数字相乘，例如，我想将工时和每小时费率相乘...然后将该数字添加到所有项目的总成本中...请帮助

from django.db import models
from django.contrib.auth.models import User
from .directors import Directors

class ApprovedBudget(models.Model):
  job=models.CharField(max_length=255)
  time=models.DateTimeField()
  labourhours=models.IntegerField()
  rate=models.DecimalField(max_digits=9, decimal_places=2)
  materials=models.DecimalField(max_digits=9, decimal_places=2)
  travel=models.DecimalField(max_digits=9, decimal_places=2)
  other=models.DecimalField(max_digits=9, decimal_places=2)
  notes=models.CharField(max_length=450)
  budget=models.DecimalField(max_digits=9, decimal_places=2)
  actual=models.DecimalField(max_digits=9, decimal_places=2)
  undercover=models.DecimalField(max_digits=9, decimal_places=2)
  status = models.CharField(max_length=12,default='pending')
  #pending,approved,rejected,cancelled 
  is_approved = models.BooleanField(default=False)
  #hide
  updated = models.DateTimeField(auto_now=True, auto_now_add=False) created = models.DateTimeField(auto_now=False, auto_now_add=True)
  
  objects = Directors()

  class Meta:
    verbose_name = (ApprovedBudget)
    verbose_name_plural = ('ApprovedBudget')
  
  def __str__(self):
    return str(self.job)
  
  @property
  def labour(self):
    if(self.labourhours != None ):
      labour=self.labourhours*self.rate
      return labour

Answer 1

您可以通过覆盖模型的save() 方法来做到这一点。
首先在模型中添加一个额外的字段来存储这样的乘法值

class ApprovedBudget(models.Model):
    .....all other fields
    labour = models.IntegerField(blank=True)#set blank=True so it will not raise any validation error while creating object

    def save(self, *args, **kwargs):
        if(self.labourhours != None ):
        self.labour=self.labourhours*self.rate
        super(ApprovedBudget, self).save(*args, **kwargs)

如果您不想将其存储在数据库中而只想在管理界面上显示而不是这样

from django.contrib import admin

class ApprovedBudgetAdmin(admin.ModelAdmin):
      list_display = [..all your fields, 'labour_cost']
      
      def labour_cost(self, obj):
          if obj.labourhours and obj.rate:
             return self.labourhours*self.rate
          return 'None'