python django 使用 lambda 和 if 语句进行排序

Question

我有日期和一些美元总模型:

class FirstDate(models.Model):
    gross = models.DecimalField(max_digits=12, decimal_places=2, default=0)
    updated = models.DateTimeField(auto_now=True)

class SecondDate(models.Model):
    gross = models.DecimalField(max_digits=12, decimal_places=2, default=0)
    updated = models.DateTimeField(auto_now=True)

并且想按gross排序，如果gross相同，则用updated字段排序

例如，

qs1 = SoloDate.objects.all()[:2]
qs2 = GroupDate.objects.all()[:2]

result_list = sorted(
    chain(qs1, qs2),
    key=lambda x: x.gross # and if gross is the same, for the gross same objects, x.updated and then update was also the same, x.pk,
    reverse=True
)

我的意思是，有两个对象分别来自 qs1 和 qs2。

# objects from qs1
qs1_obj1 = {
'pk': 1,
'gross': 5,
'updated': 2018-11-24 10:53:23.360707+00:00
}

qs1_obj2 = {
'pk': 2,
'gross': 5,
'updated': 2018-11-25 10:53:23.360707+00:00
}

# objects from qs2
qs2_obj1 = {
'pk': 3,
'gross': 5,
'updated': 2018-11-24 10:53:23.360707+00:00
}

qs2_obj2 = {
'pk': 4,
'gross': 1,
'updated': 2018-11-23 10:53:23.360707+00:00
}

其 result_list 顺序为 qs1_obj1、qs2_obj1、qs1_obj2、qs_2_obj_2 .

原因是:

qs1_obj1:1.按总量，2.按更新，3.按PK，

qs2_obj1:1.by总，2.by更新，3.但pk不好，

qs1_obj2:1.bygross，2.butbydpdated迟到了，

qs2_obj2:1.gross很小。

也许这不是一个好问题或麻烦的问题，我需要帮助。

问题是:

key=lambda x: x.gross # and if gross is the same, for the same gross objects, x.updated and then update was also the same, x.pk,

我该怎么做？

Answer 1

尝试按多个字段排序，如下所示:

result_list = sorted(
    chain(qs1, qs2),
    <b>key=lambda x: (x.gross, -x.updated.timestamp(), x.pk)</b> # and if gross is the same, for the gross same objects, x.updated and then update was also the same, x.pk,
    reverse=True
)