>>>a=[999999,2,3]
>>>b=[999999,2,3]
>>>print(a[0] is b[0])
False#because it works for numbers -5 through 256
>>>a=[1,2,3]
>>>b=a[:]
>>>print(a[0] is b[0])
True#because it works for numbers -5 through 256
>>>a=[999999,2,3]
>>>b=a[:]
>>>print(a[0] is b[0])
True#why not False ???
发生了什么 b=a[:] (为什么不适用于数字 -5 到 256 )?