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)