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

Guido van Rossum guido at python.org
Wed May 25 01:48:16 EDT 2016

Well, ZeroDivisionError doesn't derive from ValueError, does it? So it may
not be a good idea, but it's certainly a tradition.

On Tuesday, May 24, 2016, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

> 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.
> --
> Greg
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--Guido (mobile)
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