class Vec: """ A simple vector class Instances of the Vec class can be constructed from numbers >>> a = Vec(1, 2, 3) >>> b = Vec(3, 2, 1) added >>> a + b Vec(4, 4, 4) subtracted >>> a - b Vec(-2, 0, 2) and multiplied by a scalar on the left >>> 3.0 * a Vec(3.0, 6.0, 9.0) or on the right >>> a * 3.0 Vec(3.0, 6.0, 9.0) """ def __init__(self, *v): self.v = list(v) @classmethod def fromlist(cls, v): if not isinstance(v, list): raise TypeError inst = cls() inst.v = v return inst def __repr__(self): args = ', '.join(repr(x) for x in self.v) return 'Vec({0})'.format(args) def __len__(self): return len(self.v) def __getitem__(self, i): return self.v[i] def __add__(self, other): # Element-wise addition v = [x + y for x, y in zip(self.v, other.v)] return Vec.fromlist(v) def __sub__(self, other): # Element-wise subtraction v = [x - y for x, y in zip(self.v, other.v)] return Vec.fromlist(v) def __mul__(self, scalar): # Multiply by scalar v = [x * scalar for x in self.v] return Vec.fromlist(v) __rmul__ = __mul__ def test(): import doctest doctest.testmod() test()