JLundell wrote:
I've got a subclass of fractions.Fraction called Value; it's a mostly
trivial class, except that it overrides __eq__ to mean 'nearly equal'.
However, since Fraction's operations result in a Fraction, not a
Value, I end up with stuff like this:
x = Value(1) + Value(2)
where x is now a Fraction, not a Value, and x == y uses
Fraction.__eq__ rather than Value.__eq__.
This appears to be standard Python behavior (int does the same thing).
I've worked around it by overriding __add__, etc, with functions that
invoke Fraction but coerce the result. But that's tedious; there are a
lot of methods to override.
So I'm wondering: is there a more efficient way to accomplish what I'm
after?
I would change the approach.
To the question, "*is* a Value a Fraction", some may tempted to answer
"No" (for instance, a fraction has a denominator, a value has not).
However "Does a Fraction *have* a Value", you could possibly say "Yes".
The value may be then an attribute of the class Fraction, not a subclass.
To test fraction equality, use F1 == F2. In order to test 'nearly
equality', use F1.val() == F2.val().
JM
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