Pandas Dataframe可按列对dict分组 [英] Pandas Dataframe to dict grouping by column

问题描述

我有一个像这样的数据框:

I have a dataframe like this:

Subject_id    Subject    Score    
Subject_1        Math        5                 
Subject_1    Language        4                 
Subject_1       Music        8
Subject_2        Math        8                 
Subject_2    Language        3                 
Subject_2       Music        9

我想将其转换为字典，按subject_id分组

And I want to convert it into a dictionary, grouping by subject_id

{'Subject_1': {'Math': 5,
               'Language': 4,
               'Music': 8},
{'Subject_2': {'Math': 8,
               'Language': 3,
               'Music': 9}
}

如果我只有一个主题，那么我可以这样做:

If I would have only one Subject, then I could so:

my_dict['Subject_1'] = dict(zip(df['Subject'],df['Score']))

但是由于我有几个主题，所以按键列表重复出现，所以我不能直接使用zip.

But since I have several subjects the list of keys repeats, so I cannot use directly a zip.

数据框具有.to_dict('index')方法，但是创建字典时我需要能够按特定列进行分组.

Dataframes has a .to_dict('index') method but I need to be able to group by a certain column when creating the dictionary.

我该如何实现?

谢谢.

推荐答案

使用 groupby ，最后将输出转换为Series 详细信息:

print (df.groupby('Subject_id').apply(lambda x: dict(zip(x['Subject'],x['Score']))))

Subject_id
Subject_1    {'Math': 5, 'Music': 8, 'Language': 4}
Subject_2    {'Math': 8, 'Music': 9, 'Language': 3}
dtype: object

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