'float' 对象在 Django 查询集中不可迭代

Question

class TransactionHistoryListSerializer(serializers.BaseSerializer):
    class Meta:
        model = CustomerVisit

    def to_representation(self, instance):

        price = 0
        package_price = booking_models.TestBooking.objects.filter(customer_visit=instance).values_list(
            "package__test__test_mrp", flat=True
        )[0]
        for price in package_price:
            pass

        return {
            "visit_id": instance.id,
            "customer_name": {
                "salutation": instance.customer.salutation,
                "first_name": instance.customer.first_name,
                "middle_name": instance.customer.middle_name,
                "last_name": instance.customer.last_name,
            },
            "dob": instance.customer.date_of_birth,
            "amount": sum([k.amount for k in booking_models.TestBooking.objects.filter(customer_visit=instance)])
            + (price if price else 0),
            "discount": sum([k.discount for k in booking_models.TestBooking.objects.filter(customer_visit=instance)]),
            "paid_amount": sum([k.amount for k in payment_models.Payment.objects.filter(customer_visit=instance)]),
        }

这里 tes_mrp 是浮点型。 我搜索并获得了使用列表理解的解决方案，但仍然无法正常工作。我试过[[price] for price in package_price]，for price in package_price: a = list(str(price))，但仍然得到浮动对象是不可迭代的。我肯定做错了什么。有人可以帮忙吗。谢谢！！

Answer 1

这是导致这一行的原因 - 对于 package_price 中的价格：

好吧，那是因为你在做.values_list(..., flat=True)，它返回一个列表，然后用[0] 对其进行索引，所以你得到了第一个值。 package_price 因此确实是一个浮点数，正如错误所说，您不能迭代单个浮点数。

因此，只需取出 [0] 即可修复该特定位。

您的代码可以简化为不重复查询并使用 Django 的聚合：

def to_representation(self, instance):
    bookings = booking_models.TestBooking.objects.filter(customer_visit=instance)
    payments = payment_models.Payment.objects.filter(customer_visit=instance)

    package_price = bookings.values_list("package__test__test_mrp", flat=True).first()
    booking_amounts = bookings.aggregate(
        price_sum=Sum("amount"),
        discount_sum=Sum("discount"),
    )
    payment_amounts = payments.aggregate(
        payment_sum=Sum("amount"),
    )

    return {
        "visit_id": instance.id,
        "customer_name": {
            "salutation": instance.customer.salutation,
            "first_name": instance.customer.first_name,
            "middle_name": instance.customer.middle_name,
            "last_name": instance.customer.last_name,
        },
        "dob": instance.customer.date_of_birth,
        "amount": (booking_amounts.get("price_sum") or 0) + package_price,
        "discount": booking_amounts.get("discount_sum") or 0,
        "paid_amount": payment_amounts.get("payment_sum") or 0,
    }