又名余弦相似度，代码如下：
import mathdef cos_dist(a, b): if len(a) != len(b): return None part_up = 0.0 a_sq = 0.0 b_sq = 0.0 for a1, b1 in zip(a,b): part_up += a1*b1 a_sq += a1**2 b_sq += b1**2 part_down = math.sqrt(a_sq*b_sq) if part_down == 0.0: return None else: return part_up / part_downif __name__ == "__main__": #d1 = (0.5, 0.8, 0.3) #d2 = (0.9, 0.4, 0.2) #q = (1.5, 1.0, 0) d1 = (0.1, 0, 0.3) d2 = (0, 0.9, 0.4) q = (0, 0.8, 0.5) print cos_dist(d1, q) print cos_dist(d2, q)
原文地址：Python计算N维向量的余弦夹角。, 感谢原作者分享。 玩坏了可以选择重来，
