您的最后一个示例可能适用于某些工作：
--
class Job(models.Model):
veryImportant = models.IntegerField()
def get_fee():
return 2 * veryImportant
class Report(models.Model):
job = models.ForeignKey(Job)
overridableFee = models.DecimalField(max_digits=7, decimal_places=2)
def __init__(self, *args, **kwargs):
super(Report, self).__init__(*args, **kwargs)
if not self.id:
self.overridableFee = self.job.get_fee()
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