python技巧 is 和 ==

• is 判断变量是否指向同一个对象
• == 判断变量引用的对象是否相等

In [2]: a=[1,2]

In [3]: b=a

In [4]: a == b
Out[4]: True

In [5]: a is b
Out[5]: True

In [6]: c = list(a)

In [7]: a == c
Out[7]: True

In [8]: a is c
Out[8]: False

In [9]: b is c
Out[9]: False