On 2016-07-06 22:17, Vincent Delecroix wrote:
> Indeed
> {{{
> sage: parent(~1) # parent changes
> Rational Field
> sage: parent(1.inverse_of_unit()) # same parent
> Integer Ring
> sage: 2.inverse_of_unit() # error
> Traceback (most recent call last):
> ...
> ZeroDivisionError: Inverse does not exist.
> }}}
> sided note: I would like the above to actually be an `ArithmeticError`
> rather than a `ZeroDivisionError`.
I agree that it is in general not a ZeroDivisionError, but that it is a
(special) ArithmeticError.
Built-in exceptions (from [1]):
| +-- ArithmeticError
| | +-- FloatingPointError
| | +-- OverflowError
| | +-- ZeroDivisionError
Maybe a class
class NotInvertibleError(ArithmeticError)
would be suitable; thus one can catch exactly when something is not
invertible and not accidentally catch something else (e.g.
OverflowError, etc.).
(+ Deprecation)
Daniel
[1] https://docs.python.org/2/library/exceptions.html, bottom
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