Python的哈希性（hashable）

An object is hashable if it has a hash value which never changes during its lifetime (it needs a __hash__() method), and can be compared to other objects (it needs an __eq__() method). Hashable objects which compare equal must have the same hash value.

一个对象的哈希性是指在生命周期内不可改变（内置__hash__()方法），并且可以和其他对象比较（内置__eq__()方法），当这两个对象相等的时候具有相同的哈希值。

Hashability makes an object usable as a dictionary key and a set member, because these data structures use the hash value internally.

具有哈希性的对象才可作为字典的key和set的成员。

All of Python’s immutable built-in objects are hashable; mutable containers (such as lists or dictionaries) are not. Objects which are instances of user-defined classes are hashable by default. They all compare unequal (except with themselves), and their hash value is derived from their id().

所有不可改变的内置对象都是哈希的，可变的集合不具有哈希性（list、dictionary）用户自定义类的实例默认具有哈希性，而他们的哈希值重他们id性质中来。

 

转载于:https://my.oschina.net/avenger222/blog/3004754