每日python（3）

在读取一组数据创字典时，可以使用setdefaul函数对字典进行初始化，这样很方便呀，不用每次都检查是否为新值

比如实际任务中，我希望把以人名为key的字典改换成以movie为key的字典就可以这样写

 1 namekey_dic = {‘Lisa Rose‘: {‘Lady in the Water‘: 2.5, ‘Snakes on a Plane‘: 3.5,
 2                          ‘Just My Luck‘: 3.0, ‘Superman Returns‘: 3.5, ‘You, Me and Dupree‘: 2.5,
 3                          ‘The Night Listener‘: 3.0},
 4            ‘Gene Seymour‘: {‘Lady in the Water‘: 3.0, ‘Snakes on a Plane‘: 3.5,
 5                             ‘Just My Luck‘: 1.5, ‘Superman Returns‘: 5.0, ‘The Night Listener‘: 3.0,
 6                             ‘You, Me and Dupree‘: 3.5},
 7            ‘Michael Phillips‘: {‘Lady in the Water‘: 2.5, ‘Snakes on a Plane‘: 3.0,
 8                                 ‘Superman Returns‘: 3.5, ‘The Night Listener‘: 4.0},
 9            ‘Claudia Puig‘: {‘Snakes on a Plane‘: 3.5, ‘Just My Luck‘: 3.0,
10                             ‘The Night Listener‘: 4.5, ‘Superman Returns‘: 4.0,
11                             ‘You, Me and Dupree‘: 2.5},
12            ‘Mick LaSalle‘: {‘Lady in the Water‘: 3.0, ‘Snakes on a Plane‘: 4.0,
13                             ‘Just My Luck‘: 2.0, ‘Superman Returns‘: 3.0, ‘The Night Listener‘: 3.0,
14                             ‘You, Me and Dupree‘: 2.0},
15            ‘Jack Matthews‘: {‘Lady in the Water‘: 3.0, ‘Snakes on a Plane‘: 4.0,
16                              ‘The Night Listener‘: 3.0, ‘Superman Returns‘: 5.0, ‘You, Me and Dupree‘: 3.5},
17            ‘Toby‘: {‘Snakes on a Plane‘: 4.5, ‘You, Me and Dupree‘: 1.0, ‘Superman Returns‘: 4.0}
18            }
19
20 def transform(scorelist):
21     movielist = {}
22     for person in scorelist:
23         for movie in scorelist[person]:
24             movielist.setdefault(movie, {})
25             movielist[movie][person] = scorelist[person][movie]
26     return movielist
27
28 moviekey_dic = transform(namekey_dic)

print moviekey_dic的结果为：

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