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获取Django REST中的amount字段结果之和

django-rest-framework django python

Somil · 技术社区 · 6 年前

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

现在我想把这三个数量的总和显示出来 total 但由于上述方法计算量大,计算时间长,而且只需计算两次即可得到 全部的

我怎样才能得到 amount1 , amount2 , amount3 get_amount1 , get_amount2 , get_amount3

1 回复 | 直到 6 年前

neverwalkaloner 6 年前

你可以用 getattr 在单个序列化程序实例中:

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)

或者正如@Willem Van Onsem在评论中提到的那样 lru_cache 对于更广泛的缓存:

@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

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