bound2.py

from __future__ import division


class BoundedFloat(float):
    def __new__(self, value, minimum, maximum):
        return float.__new__(self, value)
        
    def __init__(self, value, minimum, maximum):
        if not (minimum <= value <= maximum):
            raise ValueError("Minimum must be less than or equal to value which"
                             " must be less than or equal to maximum.")
        float.__init__(value)
        self.minimum = minimum
        self.maximum = maximum

    @classmethod
    def _limit_inplace_ops(cls):
        limit_ops = ["__iadd__", "__isub__", "__imul__", "__itruediv__",
                     "__ifloordiv__", "__ipow__", "__imod__"]
        for op in limit_ops:
            setattr(cls, op, cls._limit(getattr(cls, op.replace("i", "", 1))))

    @classmethod
    def _limit(cls, function):
        def wrapped(self, other):
            new = function(self, other)
            if new < self.minimum:
                result = BoundedFloat(self.minimum, self.minimum, self.maximum)
            elif new > self.maximum:
                result = BoundedFloat(self.maximum, self.minimum, self.maximum)
            else:
                result = BoundedFloat(new, self.minimum, self.maximum)
            return result
        return wrapped


BoundedFloat._limit_inplace_ops()