[Python-ideas] Should decimal.InvalidOperation subclass ValueError?

Greg Ewing greg.ewing at canterbury.ac.nz
Wed May 25 01:41:13 EDT 2016

Guido van Rossum wrote:
> It's very
> common for modules to define their own root exception class.

And it's a nuisance when their exceptions only belong
to their own private hierarchy and don't participate in
any the standard classifications.

I don't think Decimal is directly to blame here, because
deriving its exceptions from ArithmeticError seems like
a reasonable thing to do. What *doesn't* seem reasonable
to me is that ArithmeticError doesn't derive from
ValueError. So far nobody has explained why that's
a good idea.


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