转换一个Django的queryset到JSON树

Question

假设我在我的模型两个表：

class Country(models.Model): 
     CountryName = models.CharField(max_length=20) 

class City(models.Model): 
     CityName = models.CharField(max_length=20) 
     Country = models.ForeignKey(Country) 

在我看来，我做一个JSON：

list = City.objects.annotate(CountryName=F('Country__CountryName')).values('CityName', 'CountryName').prefetch_related('Country') 
return HttpResponse(json.dumps([any_entry for any_entry in list])) 

在结果我收到这样的：

{[{CityName: 'Vancouver', CountryName: 'Canada'}, 
    {CityName: 'Montreal', CountryName: 'Canada'}, 
    {CityName: 'Dallas', CountryName: 'USA'}]} 

虽然我想是这样的：

{[ 
    { 
    CountryName: 'Canada', 
    Cities: [{CityName: 'Vancouver'}, 
      {CityName: 'Montreal'}] 
    }, 
    { 
    CountryName: 'USA', 
    Cities: [{CityName: 'Dallas'}] 
    } 
]} 

或者至少是：

{ 
Canada: ['vancouver','Montreal'], 
USA: ['Dallas'] 
} 

Answer 1

最后，我用下面的代码：

from collections import defaultdict 
city_list = defaultdict(list) 

for any_city in City.objects.annotate(CountryName=F('Country__CountryName')).values('CityName', 'CountryName'): 
    city_list[any_city['CountryName']].append(any_city['CityName']) 
return HttpResponse(json.dumps(city_list))