我必须修改什么魔术方法才能支持 in 运算符。这是我正在尝试做的一个例子:
class DailyPriceObj:
def __init__(self, date, product_id=None):
self.date = date
self.product_id = product_id
self.sd_buy = None
l = list()
l.append(DailyPriceObj(date="2014-01-01"))
DailyPriceObj(date="2014-01-01") in l # how to get this to return True?
换句话说，我希望我的对象“表现得像”date 属性，这样我就可以用它来查看 obj 是否在一个可交互的(date 应该是这里的唯一字段)。
请您参考如下方法:
您需要实现 __eq__(和 __hash__ 为了完整性):
class DailyPriceObj:
def __init__(self, date, product_id=None):
self.date = date
self.product_id = product_id
self.sd_buy = None
def __eq__(self, other):
return isinstance(other, self.__class__) and self.date == other.date
def __hash__(self):
return hash(self.date)
l = [DailyPriceObj(date="2014-01-01")]
s = {DailyPriceObj(date="2014-01-01")}
print(DailyPriceObj(date="2014-01-01") in l)
print(DailyPriceObj(date="2014-01-01") in s)
输出
True
True
来自 __hash__ 上的文档:
Called by built-in function hash() and for operations on members of hashed collections including set, frozenset, and dict.
__hash__()should return an integer. The only required property is that objects which compare equal have the same hash value; it is advised to mix together the hash values of the components of the object that also play a part in comparison of objects by packing them into a tuple and hashing the tuple.
