Python Django:AttributeError:“；对象没有属性“；

我试图将一个类中计算的属性转换到另一个类中。我被卡住了

在“奖励”课程中，我需要从“保证水平”中减去“免赔额”。在“质押”类中，我需要从“金额”中减去“不应纳税”以返回“可扣除的总额”

在“我的模板”中访问它时，此选项可以正常工作：

(${{ reward.deductible}} is tax deductible or ${{ reward.not_taxable }} is not tax deductible)

在服务器上运行时，我收到一个内部服务器错误：[Django]错误（外部IP）：内部服务器错误：/projects/fund/billing/1000

以下是回溯：

Internal Server Error: /projects/fund/billing/1000/
Traceback (most recent call last):
File "/var/venv/website/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/var/sites/proj/payments/views.py", line 98, in pledge_billing
html = template.render(c)
File "/var/venv/website/lib/python2.7/site-packages/django/template/backends/django.py", line 74, in render
return self.template.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 209, in render
return self._render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
return self.nodelist.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 903, in render
bit = self.render_node(node, context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
return node.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/loader_tags.py", line 135, in render
return compiled_parent._render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
return self.nodelist.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 903, in render
bit = self.render_node(node, context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
return node.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/loader_tags.py", line 65, in render
result = block.nodelist.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 903, in render
bit = self.render_node(node, context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
return node.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 957, in render
output = self.filter_expression.resolve(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 647, in resolve
obj = self.var.resolve(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 787, in resolve
value = self._resolve_lookup(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 825, in _resolve_lookup
current = getattr(current, bit)
File "/var/sites/proj/projects/models.py", line 81, in deductible_total
return self.get_deductible_total()
File "/var/sites/proj/projects/models.py", line 77, in get_deductible_total
return (self.amount - self.not_taxable)
AttributeError: 'Pledge' object has no attribute 'not_taxable'    

models.py

class Pledge(models.Model):
    project = models.ForeignKey('Project')
    amount = models.DecimalField(decimal_places=2,max_digits=10,
        default=D('0.00'))
    reward = models.ForeignKey('Reward',blank=True,null=True,
        on_delete=models.SET_NULL)

    objects = PledgeManager()

    def get_deductible_total(self):
        return (self.amount - self.not_taxable) 

    @property
    def deductible_total(self):
        return self.get_deductible_total()


class Reward(models.Model):
    project = models.ForeignKey('Project')
    title = models.CharField(max_length=255)
    pledge_level = models.DecimalField(decimal_places=2, max_digits=10)
    deductible = models.DecimalField(decimal_places=2, max_digits=10)
    description = models.TextField(blank=True)

    def get_not_taxable(self):
        return (self.pledge_level - self.deductible)

    @property
    def not_taxable(self):
        return self.get_not_taxable()

因为我在项目应用程序中编辑models.py文件，所以我在项目上进行了迁移。也许由于项目的变化，支付应用程序也需要在其上运行迁移

---

非常感谢你的帮助

更改方法如下：

def get_deductible_total(self):
    return (self.amount - self.reward.not_taxable) 

顺便说一句，通常分离属性和方法是没有意义的，您也可以在属性内部进行计算。你本来可以

@property
def deductible_total(self):
    return (self.amount - self.not_taxable) 

但将它们分开的一些原因：
1） 属性不会引发错误，因此如果您在需要异常的其他地方调用它，则将它们分开是有意义的。
2） 如果出于某种原因需要一个返回结果的方法（或函数，基本上是可调用的），那么还需要将它们分开。可能不是这种情况，可以使用

lambda

s进行打击。

---

仅供参考。

奖励=型号。外键

。似乎不是一个

奖励对象。或者我错过了什么。@Jean-Françoisfare对不起，我没抓住你的重点。它还会是什么（当然，除非为空）？我的意思是，奖励的类别不是奖励。检查初始标记为@makaveli的答案。。。谢谢你的解释和建议！还想指出的是，我必须检查物品是否有奖励（有可能有一个没有奖励的承诺）<代码>def获取可扣除总额（自我）：如果不是自我奖励：返回D（'0'）返回（自我金额-自我奖励。不征税）