Django ManyToMany 字段管理员显示最高值

Question

I want to know how I can display the "highest value" from my ManyToMany Field in the admin. This is my models.py file:

class Personal(models.Model):
    lastname  = models.CharField(max_length = 100)
    firstname = models.CharField(max_length = 100)
    degree = models.ManyToManyField('Degree')
    
    def __str__(self):
        return self.lastname

class Degree(models.Model):
    name_degree = models.CharField(verbose_name = 'Degree', max_length = 200, blank = False)
    rank = models.PositiveIntegerField(default = 0)

    def __str__(self):
        return self.name_degree

In my backed, I have created different types of Degree's, all with a "ranking". In my case, the highest degree you can have is "Doctoral Degree", with a rank of "6".

So if a User is creating himself in "Personal" he will have the option to select all the Degree's he has achieved. But for my Personal list, I just to want to see the highest one, eg if the User selects "Bachelor's Degree" and "Master's Degree", the Personal list should only contain "Master's Degree", because 5 > 4.

Someone with an idea on how my admin.py file should look like?

class PersonalAdmin(admin.ModelAdmin):
    list_display = ('lastname', 'firstname', ) # 'degree'

Answer 1

You can annotate the QuerySet with the highest degree, and then define a method that will render that maximum:

from django.db.models import Max

class MyModelAdmin(admin.ModelAdmin):
    list_display = ['lastname', 'firstname', ]

    def get_queryset(self, request):
        queryset = super().get_queryset(request).annotate(
            
        )

    def (self, obj):
        return obj.max_degree