[Tutor] Python __del__ method

[eryk sun]

On Tue, Jul 11, 2017 at 2:47 PM, Jia Yue Kee <JiaYue.Kee at firstsolar.com> wrote:
>
> Case 2: If I were to run the code in "Interactive Mode", the following output will be obtained:
>
>>>> x = Robot("Tik-Tok")
> Tik-Tok has been created!
>>>> y = Robot("Jenkins")
> Jenkins has been created!
>>>> z = x
>>>> z
> <__main__.Robot object at 0x02D7E910>
>>>> x
> <__main__.Robot object at 0x02D7E910>
>>>> del x
>>>> del z
>>>> del y
> Robot has been destroyed
>
> My question being why is that "Robot has been destroyed" is only printed once in Case 2
> (interactive mode) while it is printed out twice in Case 1 (script mode)?

The REPL (interactive mode) keeps a reference to the last non-None
result as builtins `_`, for convenient access to the last result. In
your case, it results from evaluating `x`. Thus you have a hidden
reference that's keeping that object alive. Enter anything except None
or _ to clear that reference.