Python内置函数id

英文文档：

id(object)

Return the “identity” of an object. This is an integer which is guaranteed to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the sameid() value.

CPython implementation detail: This is the address of the object in memory.

说明：

　　1. 返回对象的唯一标识符，用整数表示。在程序生命周期内，这个标识符常量是唯一的。

>>> a = 1
>>> id(a)
>>> id(1.0)
>>> a = 'some text'
>>> id(a)