Question

我有这个数据结构：

class Currency(Model):
    name = CharField()
    ...

class Invoice(Model):
    currency = ForeignKey(Currency)
    ...

我想按Invoices过滤所有Currencies个分组。我希望结果是这样的：

{
    'USD': '<INVOICES_QUERYSET_FOR_USD>',
    'EUR': '<INVOICES_QUERYSET_FOR_EUR>',
    ...
}

有没有简单的方法来实现这一点，还是我必须自己安装字典？我知道Annotate给出了类似的结果，但我只是想用一个公共属性值对Queryset进行分组。

Answer 1

这样的东西可以让你得到你想要的东西。

from collections import defaultdict

currencies_of_interest = [ 'USD', 'EUR', ]
qs = Invoice.objects.select_related(
    'currency'
).filter(
    currency__name__in = currencies_of_interest
)order_by('currency__name')
currencies = defaultdict(list)
for x in qs:
    currencies[x.currency.name].append(x)
# now currencies will look like:
# {
#    'USD': list[Invoice] for USD,
#    'EUR': list[Invoice] for EUR,
#     ...
# }

如果您更喜欢使用查询集，并且不介意对数据库进行多次查询：

currencies_of_interest = [ 'USD', 'EUR', ]
currencies = {}
for x in currencies_of_interest:
    currencies[x] = Invoice.objects.select_related(
        'currency').filter(currency__name=x)
# now currencies will look like:
# {
#    'USD': QuerySet[Invoice] for USD,
#    'EUR': QuerySet[Invoice] for EUR,
#     ...
# }

如何在Django中按属性对查询集进行分组

1 个答案: