正在调用\uUu hash_Uu（）方法

Question

我定义类MyClass()

import random
class MyClass():
    def __init__(self, value):
        self.value = value
    def __hash__(self):
        return random.randin(1, 10) 
x = MyClass() 

我知道，在我声明x = MyClass()之后，__init__是自动调用的。但是__hash__呢？它在没有被x.__hash__()显式调用的情况下工作吗？
每个以__开头的方法是自动调用的还是程序决定何时调用它们？
为了找到答案，我查阅了许多文件，但都没有成功。在

谢谢你的回答！在

Answer 1

来自Python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;

参考号：https://docs.python.org/3/reference/datamodel.html#object.__hash__

另外，请不要从\uuHash_Uu（）返回随机数。在

Answer 2

否，__hash__不会自动调用。看看the documentation for this method：

Called by built-in function hash() and for operations on members of hashed collections including set, frozenset, and dict.

因此，如果有人hash(x)，将调用此方法。在

顺便说一句，返回一个随机数是个坏主意：

The only required property is that objects which compare equal have the same hash value