recommendations.py 文件源码

def sim_distance(prefs,person1,person2):
    # shared-items ??    
    si ={}
    for item in prefs[person1]:
        if item in prefs[person2]:
            si[item]=1

    #??????????????0
    if(len(si)==0):
        return 0

    #??share-items???????
    sum_of_squares = sum([pow(prefs[person1][item]-prefs[person2][item],2) 
                        for item in si])

    return 1/(1+sqrt(sum_of_squares))