Django snippets

from django.contrib import admin

class InlineWithLimitedManyToManyFields(admin.StackedInline):
    limited_manytomany_fields = {}
    
    def get_formset(self, request, obj=None, **kwargs):
        # Hack! Hook parent obj just in time to use in formfield_for_manytomany
        self.parent_obj = obj
        return super(InlineWithLimitedManyToManyFields, self).get_formset(
            request, obj, **kwargs)
    
    def formfield_for_manytomany(self, db_field, request, **kwargs):
        if db_field.name in self.limited_manytomany_fields.keys() and \
               hasattr(self,'parent_obj'):
            kwargs['queryset'] = db_field.rel.to.objects.filter(**{
                self.limited_manytomany_fields[db_field.name]: self.parent_obj
                })
        return super(
            InlineWithLimitedManyToManyFields, self).formfield_for_manytomany(
            db_field, request, **kwargs)


class ExampleInline(InlineWithLimitedManyToManyFields):
    model = ExampleModel
    limited_manytomany_fields = {
        'first_many_to_many_field_name':
            'field_name_for_foreignkey_in_related_model_to_parent',
        'second_many_to_many_field_name':
            'field_name_for_foreignkey_in_related_model_to_parent',
        }