如何在python的迭代中为空嵌套字典添加值[关闭]

Question

我想计算用户之间的相似度，但不能将值添加到空字典中。

这是我的代码：

data={'Lisa Rose': {'Lady in the Water': 2.5, 'Snakes on a Plane': 3.5,  
'Just My Luck': 3.0, 'Superman Returns': 3.5, 'You, Me and Dupree': 2.5},  
'Gene Seymour': {'Lady in the Water': 3.0, 'Snakes on a Plane': 3.5,   
'Just My Luck': 1.5, 'The Night Listener': 3.0},   
'Michael Phillips': {'Lady in the Water': 2.5, 'Snakes on a Plane': 3.0,  
'Superman Returns': 3.5, 'The Night Listener': 4.0},  
'Claudia Puig': {'Snakes on a Plane': 3.5, 'Just My Luck': 3.0,  
'The Night Listener': 4.5, 'You, Me and Dupree': 2.5},  
'Mick LaSalle': {'Just My Luck': 2.0, 'Lady in the Water': 3.0,'Superman 
 Returns': 3.0, 'The Night Listener': 3.0, 'You, Me and Dupree': 2.0},   
'Jack Matthews': {'Snakes on a Plane': 4.0, 'The Night Listener': 3.0, 
'Superman Returns': 5.0, 'You, Me and Dupree': 3.5},  
'Toby': {'Snakes on a Plane':4.5,'You, Me and Dupree':1.0,'Superman 
 Returns':4.0}}

 df = pd.DataFrame(data)`

 def usersimilarity(df):
     w = dict()
     for u in df.keys():
        for v in df.keys():
            if u == v:
                continue
            w[u][v] = 
   len(set(df[u])&set(df[v]))/math.sqrt(len(df[u])*len(df[v])*1.0)
return w

Answer 1

你想这样做吗？

def usersimilarity(df):
    w = dict()
    for u in df.keys():
        for v in df.keys():
            if u == v:
                continue
            if u not in w.keys():
                w[u] = dict()
            w[u][v] = len(set(train[u])&set(train[v]))/math.sqrt(len(train[u])*len(train[v])*1.0)
    return w

当你做w[u][v]时，[v]正在访问一些不存在的东西。你必须先创建[u]。