Re: A proposal to modify `None` so that it hashes to a constant

You are absolutely right, of course.  It was a wild idea, and a bad one.
I find myself moving towards supporting the OP.  I can't see anything 
terrible about the hash of None always being 0, or perhaps better some 
other arbitrary constant.
Rob

On 04/12/2022 03:20, Steven D'Aprano wrote:
> On Thu, Dec 01, 2022 at 10:18:49PM +0000, Rob Cliffe via Python-Dev wrote:
>
>> Wild suggestion:
>>      Make None.__hash__ writable.
>> E.g.
>>      None.__hash__ = lambda : 0 # Currently raises AttributeError:
>> 'NoneType' object attribute '__hash__' is read-only
> You would have to write to `type(None).__hash__` because of the way
> dunders work.
>
> Now imagine that you have twenty different libraries or functions or
> classes, each the `__hash__` method to a different function. Chaos.
>
> You can simulate that chaos with this:
>
> ```
> import random
>
> class ChangingHash:
>      def __repr__(self):
>          return "MyNone"
>      def __hash__(self):
>          # Simulate the effect of many different callers changing
>          # the hash value returned at unpredictable times.
>          return random.randint(1, 9)
>
> MyNone = ChangingHash()
>
> data = {MyNone: 100}
> print(MyNone in data)  # 8 in 9 chance of printing False
> data[MyNone] = 200
> print(data)  # 8 in 9 chance of {MyNone: 100, MyNone: 200}
> print(MyNone in data)  # now 7 in 9 chance of printing False
> ```
>
>

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