一段简单实现【余弦相似度】的python代码

<pre name="code" class="python">def cos(vector1,vector2):    dot_product = 0.0    normA = 0.0    normB = 0.0    for a,b in zip(vector1,vector2):        dot_product += a*b        normA += a**2        normB += b**2    if normA == 0.0 or normB==0.0:        return None    else:        return dot_product / ((normA*normB)**0.5)