inheritance

Duncan Smith buzzard at urubu.freeserve.co.uk
Thu Jun 12 17:46:15 CEST 2003


I'm in the process of subclassing some functionality of a class that was
getting a bit too big.  But a lot of the inherited functions (eg. __mul__())
return objects of the parent type.  Initially I had the following code...


class Table(table.NumTable):
    def __init__(self, values, variables, id = None):
        table.NumTable.__init__(self, values, variables, id)
        self.isBarnardised = 0
        self.isRandRounded = 0
        self.isConvRounded = 0


    def __mul__(self, other):
        res = table.NumTable.__mul__(self, other)

        return Table(res.values, res.variables)


But I have ended up with this ...


class Table(table.NumTable):
    isBarnardised = 0
    isRandRounded = 0
    isConvRounded = 0


    def __mul__(self, other):
        res = table.NumTable.__mul__(self, other)

        return Table(res.values, res.variables)


The questions I have are:

Is there any practical difference between the two?

Is there any alternative to explicitly overloading each of the parent class
functions that return a new instance?

Cheers.

Duncan






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