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

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
```


-- 
Steve