When are immutable tuples *essential*? Why can't you just use lists *everywhere* instead?

[Neil Cerutti]

On 2007-04-23, Steve Holden <steve at holdenweb.com> wrote:
> Neil Cerutti wrote:
>> So the question becomes: Why do Python dictionaries require
>> keys to be of an immutable type?
>
> Because otherwise people would expect to be able to use a list
> to select a dictionary entry even after they'd modified
> elements of the list after creating the dictionary entry. Which
> they couldn't. So Python doesn't let them use lists.

The interpreter explains it: "A list is not a hashable object."
Choosing a hash table instead of some kind of balanced tree seems
to be just an optimization. ;)

-- 
Neil Cerutti