immutablevector.py

import math

class ImmutableVector(object):
    __slots__ = ('_d',)
    def __init__(self, x, y):
        object.__setattr__(self, _d, (x, y))
    def __setattr__(self, n, v):
        raise ValueError("Can't alter instance of %s" % type(self))
    @property
    def x(self): 
        return self._d[0]
    @property
    def y(self):
        return self._d[1]
    def __eq__(self, other):
        return self._d == other._d
    def __ne__(self, other):
        return self._d != other._d
    def __hash__(self):
        return hash(self._d)
    def __add__(self, other):
        return type(self)(self.x+other.x, self.y+other.y)
    def __mul__(self, scalar):
        return type(self)(self.x*scalar, self.y*scalar)
    def __repr__(self):
        return '%s(%s, %s)' % (type(self).__name__, self.x, self.y)
    def __abs__(self):
        return math.hypot(self.x, self.y)
#.