OO Example: Fractions

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Using the Fraction class This is enough for us to create a Fraction object● a.k.a. “create a Fraction instance”● a.k.a. “instantiate the Fraction class” f1 = Fraction(2, 3) print f1 # “2 / 3” We can't do much with our Fraction object yet,so the next step is to implement some methods Multiple methods may want to check theconstraint of denom ≠ 0: make a helper methodCMPT140: <strong>OO</strong>: fractions 20 Nov 20094
Helper: check constraints Constraint: denom should never be 0 Don't want this to be publicly-accessible, sostart name with '__' (double-underscore):hidden from view in Python● In C++/Java, can declare it 'private' def __check(self): How to flag error? Use exceptions!➢ if denom == 0:● raise ZeroDivisionError● Up to whoever is using this Fraction tohandle the errorCMPT140: <strong>OO</strong>: fractions 20 Nov 20095
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OO Example: Fractions

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