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

[Rob Cliffe]

Or more generally, any operation on multiple values, where each value is 
valid individually, but the result of the operation is not:

 >>> p = Decimal('1E999999999')

 >>> q = Decimal('10')

 >>> try:

...     p*q

... except ArithmeticError:

...     print 'ArithmeticError'

...

ArithmeticError



On 25/05/2016 06:48, Guido van Rossum wrote:
> 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 
> <mailto: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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