Iris cubes and coordinates are both mutable and hashable

[shoyer]

This break Python conventions and thus is likely to lead to unexpected behavior.

This is especially problematic because these objects also implement their own __eq__ method, and thus hashes for equal objects are not necessary equal.

For an overview, read the answers on this StackOverflow question:
http://stackoverflow.com/questions/2671376/hashable-immutable

Since it's unlikely that cubes or coords can be made entirely immutable, my suggested fix is to add __hash__ = None to both Coord and Cube.

[rhattersley]

👍

[pelson]

Got done in #1772 I believe.

[djkirkham]

It's still an issue. For both Cubes and Coords, __eq__ is based on mutable properties of the object, which implies they shouldn't be hash-able. Unless we make Cubes and Coords immutable, we shouldn't really be using them in sets or as dictionary keys.

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