cosine.py

def vector_len(v: Vector) -> float:
    return math.sqrt(sum([x*x for x in v]))

def dot_product(v1: Vector, v2: Vector) -> float:
    assert len(v1) == len(v2)
    return sum([x*y for (x,y) in zip(v1, v2)])

def cosine_similarity(v1: Vector, v2: Vector) -> float:
    """
    Returns the cosine of the angle between the two vectors.
    Results range from -1 (very different) to 1 (very similar).
    """
    return dot_product(v1, v2) / (vector_len(v1) * vector_len(v2))