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Python Object-Oriented Python Advanced Objects Multiplication

Igor Dias
Igor Dias
5,155 Points
Posted by Igor Dias
Igor Dias
5,155 Points

What's the difference between multiply self or self.value inside the method?

Inside the rmul() method when I multiply other only by self it returns a numerical multiplication. On the order hand, if I multiply other by self.value it returns string multiplication. Whats the difference between the cases?

numstring.py 
class NumString:
    def __init__(self, value):
        self.value = str(value)

    def __str__(self):
         return self.value

    def __int__(self):
        return int(self.value)

    def __float__(self):
        return float(self.value)

    def __add__(self, other):
        if '.' in self.value:
            return float(self) + other
        return int(self) + other

    def __radd__(self, other):
        return self + other

    def __iadd__(self, other):
        self.value = self + other
        return self.value

    def __mul__(self, other):
        if '.' in self.value:
            return float(self) * other
        return int(self.value) * other

    def __rmul__(self, other):
        return self * other

#    def __rmul__(self, other):
#        if '.' in self.value or '.' in other:
#            return float(self) * other
#        return int(self) * other

1 Answer

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

The internal value is stored as a string; but when you refer to the object itself, the internal conversion method is implicitly invoked for you to make it a number.

Igor Dias
Igor Dias
5,155 Points
Igor Dias
Igor Dias
5,155 Points

Thank you, Parker!

Would you mind explaining me a little more?

This internal conversion method that you refer is the __ int _() method or the _ float __() method? Or another one? Because when I pass a string as argument the multiplication returns an int. Why not a float?

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

It gets converted based on the contents, and what you multiply it with. Try passing it a value with a decimal point.