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之前创建的对象我想两个物体之间的增量:获得在该对象
class Point(models.Model):
measurement = models.ForeignKey(Measurement)
time = models.DateTimeField()
value = models.FloatField()
def delta(self):
measurement = self.measurement.point_set.order_by('time')
measurement = measurement[-2]
return self.value - measurement.value
但这显然只是适用于最新的对象。有没有办法从时间意义上获得self.object的前辈?