Is a tuple, that includes a list actually mutable?

Question

I saw a checklist type quiz.
It asked to choose all the mutable objects from a list.
There was a tuple with list as item.
I included it, because it's inner element can be changed and thus mutable,
that caused the result to be wrong.
I later checked the right answers and it was not selected as right answer.

Is the quiz or I wrong? Is an immutable iterator with mutable item mutable or immutable?

Answer 1

The tuple itself is not mutable, no. If you change the list within, you have not touched the tuple so it all checks out.

I see you have done some C and C++, it may be helpful to think about the inner list as a pointer. The tuple only holds the pointer and doesn't really care about what is happening with the mutable content that is being pointed to.

Answer 2

I've created a code, you can experiment with it.....
https://code.sololearn.com/c1ln32A7tFkE/?ref=app

Answer 3

Tuples are immutable whatever elements they contain. How the immutable tuple can contain a mutable item? It is a result of memory management in Python. In simple words any variable is a reference to the object in Python. So the tuple store a reference to the list. When the list changes ths reference stays the same.

Answer 4

portpass You can't for example include immutable iterators with mutable items as dictionary keys.

Answer 5

Seb TheS Yes, the same thing with sets. And there's a reason for that. Python calculates hashes of the dictonary keys to quick access to the dictionary. These hashes must not be changeable for dictonary keys.