Question

这是我的序列化器：

class MySerializer(serializers.Serializer): 
    amount1 = serializers.SerializerMethodField(read_only=True)
    amount2 = serializers.SerializerMethodField(read_only=True)
    amount3 = serializers.SerializerMethodField(read_only=True)
    total = serializers.SerializerMethodField(read_only=True)

    class Meta:
        model = Amount
        fields = "__all__"

    def get_amount1(self,obj):
        """very large calculation here"""
        return 5

    def get_amount2(self,obj):
        """very large calculation here"""
        return 10

    def get_amount3(self,obj):
        """very large calculation here"""
        return 15

    def get_total(self,obj):
        return self.get_amount1 +self.get_amount2+self.get_amount3

现在，我想在total字段中显示所有三个金额的总和，但是由于上述方法中的大量计算，这花费了太多时间，并且它们只为获得total而计算了两次

如何在不计算两次amount1，amount2，amount3的情况下获得get_amount1，get_amount2，get_amount3的总和？

Answer 1

您可以在单个序列化程序实例中使用getattr：

def get_amount1(self,obj):
    """very large calculation here"""
    if getattr(self, 'amount1', None):
        return self.amount1
    self.amount1 = 5
    return self.amount1

def get_amount2(self,obj):
    """very large calculation here"""
    if getattr(self, 'amount2', None):
        return self.amount2
    self.amount2 = 10
    return self.amount2

def get_amount3(self,obj):
    """very large calculation here"""
    if getattr(self, 'amount3', None):
        return self.amount3
    self.amount3 = 15
    return self.amount4

def get_total(self,obj):
    return self.get_amount1(obj) +self.get_amount2(obj)+self.get_amount3(obj)

或者如评论lru_cache中提到的@ Willem-Van-Onsem所述，以获得更广泛的缓存：

@lru_cache
def get_amount1(self,obj):
    """very large calculation here"""
    return 5

@lru_cache
def get_amount2(self,obj):
    """very large calculation here"""
    return 10

@lru_cache
def get_amount3(self,obj):
    """very large calculation here"""
    return 15

在Django REST中获取数量字段的总和

1 个答案: