Django筛选器dopdown菜单有效选择错误

Question

i have a dataset with population by year and i need to it filter by year. it works with input value but it doesn't work with dropdown menu. it gives the error "Select a valid choice. That choice is not one of the available choices."

models.py

class Pyramid(models.Model):
   year = models.IntegerField(default=0)
   city = models.CharField(max_length=15)
   men_population = models.IntegerField(default=0)
   women_population = models.IntegerField(default=0)

filters.py

import django_filters
from .models import Pyramid

class YearFilter(django_filters.FilterSet):
    year_f = django_filters.ModelChoiceFilter(queryset=Pyramid.objects.values_list('year',flat=True).distinct())
    class Meta:
        model = Pyramid
        fields = ['year_f ']

views.py

def Pyramid(request):
    dataset = models.Pyramid.objects.all()
    year_filter = YearFilter(request.GET, queryset=dataset)
    context = {
        'dataset': dataset,
        'filter': year_filter,
    }
    return render(request, 'pyramid.html', context)

it shows me the year what i enter but gives error "Select a valid choice. That choice is not one of the available choices."

Answer 1

Thank you @dirkgroten i should define years from database firstly so i add code below and it works

class YearChoiceFilter(django_filters.ChoiceFilter):
    @property
    def field(self):
        self.extra['choices'] = [(a.Year, a.Year) for a in self.parent.queryset]
        return super(YearChoiceFilter, self).field

class YearFilter(django_filters.FilterSet):
    Year = YearChoiceFilter(field_name='Year')
    class Meta:
        model = Pyramid
        fields = ['Year']

so now i wonder that can i add default year as 2018 for filter?