[hathawsh]

This is where Pythonistas rely on the idea that "we're all consenting adults here". It's very useful to let objects assert that they have an arbitrary, immutable hash value. I've used that ability in Python and it solved problems that would have been very challenging otherwise. Of course, that ability also leads to undocumented behavior if hash values change. Python coders expect dicts to behave in undocumented ways when object hashes change, but it would be a bug if that led to a segfault or a C assertion failure.

[phaedrus]

I'm genuinely curious how/why this is a problem for Python yet I've never heard of it being a problem for C#. In C# you can override Object.GetHashCode(), and there's no way in C# to even express the constraint/desire "the result of GetHashCode doesn't change (especially after insertion into a container)". Yet I've never heard of anyone in C# having a problem using mutable objects in sets or dictionaries?

[hathawsh]

To be honest, most Python coders probably never get deep enough in the language to start overriding hash values, and those who do probably understand the implications before they get that deep.