为什么python为字符串创建新对象

Question

In [38]: a = "a"
In [39]: b = "a"
In [40]: a is b
Out[40]: True
In [41]: id(a)
Out[41]: 140290557625488
In [42]: id(b)
Out[42]: 140290557625488

但是当我添加一个特殊的字符时，它正在创建一个新对象

In [43]: a = "a@"
In [44]: b = "a@"
In [45]: a is b
Out[45]: False
In [46]: id(a)
Out[46]: 140290299739112
In [47]: id(b)
Out[47]: 140290299737232

为什么它会为特殊字符显示不同的行为？