Python 根据其他字段计算的Django模型字段

围绕这一点，还有很多其他问题，但没有一个能起到作用

我希望通过

yield=start/finished

字段计算

yield

字段。我想用海图把它画出来

但是，当我通过管理门户添加对象时，它的设置是

yield=0

，并且不会计算

models.py：

class wYield(models.Model):
    starts = models.PositiveIntegerField(default=0)
    finishes = models.PositiveIntegerField(default=0)


## ONE: i've tried the below:
    yield_num = model.FloatField()
    def save(self, *args, **kwargs):
        if self.starts > 0:
             self.yield = self.finishes / self.starts 
        else:
             self.yield = 0
        super(wYield, self).save(*args, **kwargs)

## TWO: i've tried this but then I don't know how to see it in the Admin view:
    def _set_yield(self):
        if self.starts > 0:
             x = self.finishes / self.starts 
        else:
             x = 0
        return x
    yield_num = property(_set_yield)

 ## THREE: I think this works the same as TWO
    @property
    def yield_num(self):
        if self.starts > 0:
             return self.finishes / self.starts
        else:
             return 0

admin.py：

from .models import wYield

class wYieldAdmin(admin.ModelAdmin):
    list_display = ('starts', 'finishes', 'yield_num')

admin.site.register(wYield, wYieldAdmin)

---

也许你不必每次都把它保存在db上，因为它可以动态计算；否则你会浪费空间。更不用说db值的双重性了

此外，如果明天您的逻辑更改为

yield

，您将有充分的自由对

lambda

表达式执行此操作。这里有一个例子：

Class wYieldAdmin(admin.ModelAdmin):
    yield = lambda self: (self.finishes / self.starts) if self.starts > 0 else 0
    yield.short_description = 'Yield'
    list_display = ('starts', 'finishes', 'yield')

找到了答案（在AbhiP的帮助下！）Python

int

typecasting是罪魁祸首。愚蠢的问题

以下是有效的方法，允许我不保存计算字段（而是显示它并使其与模型中的字段类似）：

---

请你用更详细的解释来扩展你的答案好吗？这对理解非常有用。非常感谢。

@property
def yield_num(self):
    if self.starts > 0:
        #needed the float() to cast it out of an int
        return self.finishes / float(self.starts)
    else:
        return 0

Class wYieldAdmin(admin.ModelAdmin):
yield = lambda self: (self.finishes / self.starts) if self.starts > 0 else 0
yield.short_description = 'You have a big head'
list_display = ('starts', 'finishes', 'yield')