Django 中的自定义排序 [英] Custom ordering in Django

问题描述

如何在 Django QuerySets 中定义特定的排序?

How do you define a specific ordering in Django QuerySets?

具体来说，如果我有一个像这样的 QuerySet:['a10', 'a1', 'a2'].

Specifically, if I have a QuerySet like so: ['a10', 'a1', 'a2'].

常规订单(使用 Whatever.objects.order_by('someField'))会给我 ['a1', 'a10', 'a2']，而我正在寻找:['a1', 'a2', 'a10'].

Regular order (using Whatever.objects.order_by('someField')) will give me ['a1', 'a10', 'a2'], while I am looking for: ['a1', 'a2', 'a10'].

定义我自己的排序技术的正确方法是什么?

What is the proper way to define my own ordering technique?

推荐答案

据我所知，没有办法以这种方式指定数据库端的排序，因为它过于后端特定.您可能希望采用良好的老式 Python 排序:

As far as I'm aware, there's no way to specify database-side ordering in this way as it would be too backend-specific. You may wish to resort to good old-fashioned Python sorting:

class Foo(models.Model):
    name = models.CharField(max_length=128)

Foo.objects.create(name='a10')
Foo.objects.create(name='a1')
Foo.objects.create(name='a2')

ordered = sorted(Foo.objects.all(), key=lambda n: (n[0], int(n[1:])))
print ordered # yields a1, a2, 10

如果您发现自己经常需要这种排序，我建议为您的模型创建一个自定义的 models.Manager 子类来执行排序.类似的东西:

If you find yourself needing this kind of sorting a lot, I'd recommend making a custom models.Manager subclass for your model that performs the ordering. Something like:

class FooManager(models.Manager):
    def in_a_number_order(self, *args, **kwargs):
        qs = self.get_query_set().filter(*args, **kwargs)
        return sorted(qs, key=lambda n: (n[0], int(n[1:])))

class Foo(models.Model):
    ... as before ...
    objects = FooManager()

print Foo.objects.in_a_number_order()
print Foo.objects.in_a_number_order(id__in=[5, 4, 3]) # or any filtering expression

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