Help understanding the decisions *behind* python?

[Phillip B Oldham]

On Jul 20, 6:08 pm, Duncan Booth <duncan.bo... at invalid.invalid> wrote:
> The main reason why you need both lists and tuples is that because a tuple
> of immutable objects is itself immutable you can use it as a dictionary
> key.

Really? That sounds interesting, although I can't think of any real-
world cases where you'd use something like that.