Question

我有一个Django模型列表，我想检查字符串值是否出现在列表中ANY模型的特定字段中。请参见下面的示例：

class something:
    animals = [] #type: list[Animals]

   def does_atleast_one_animal_make_that_sound(animal_sound):
       if animal_sound in ...# for each animal in animals, turn animal.sound into a list
            print('One of the animals in the list makes this sound')
       else:
            print('No animal makes this sound')

我如何正确地用“ ...”编写函数的一部分？

Answer 1

如果数据库中存在模型实例，则可以使用任何列出的方法（第一种和第二种基于this answer中的思想）：

1）Queryset的values_list：

class something:
    animals = [] #type: list[Animals]
    animals = [animal.id for animal in animals]

    def does_atleast_one_animal_make_that_sound(animal_sound):
       if animal_sound in Animal.objects.filter(id__in=animals).values_list('sound', flat=True):
            print('One of the animals in the list makes this sound')
       else:
            print('No animal makes this sound')

2）如果您使用exists，则更好：

class something:
    animals = [] #type: list[Animals]
    animals = [animal.id for animal in animals]

    def does_atleast_one_animal_make_that_sound(animal_sound):
       if Animal.objects.filter(id__in=animals, sound=animal_sound).exists():
            print('One of the animals in the list makes this sound')
       else:
            print('No animal makes this sound')

3）如果仅构建（Animal(...)）模型，而未将其保存到数据库，则可以使用纯python过滤：

class something:
    animals = [] #type: list[Animals]

   def does_atleast_one_animal_make_that_sound(animal_sound):
       if any(filter(lambda animal: animal.sound == animal_sound, animals)):
            print('One of the animals in the list makes this sound')
       else:
            print('No animal makes this sound')

注意：通常最好将模型实例过滤委派给数据库（谈论animals变量的起源）。在这种情况下，第三个选项似乎是最好的，因为它不需要查询数据库。

如何检查值是否在Django的模型列表的字段中出现？

1 个答案: