将 pandas 数据框转换为字典 [英] convert a pandas dataframe to dictionary

问题描述

我有一个熊猫数据框，如下所示:

I have a pandas dataframe as below:

df=pd.DataFrame({'a':['red','yellow','blue'], 'b':[0,0,1], 'c':[0,1,0], 'd':[1,0,0]})
df

看起来像

    a       b   c   d
0   red     0   0   1
1   yellow  0   1   0
2   blue    1   0   0

我想将其转换为字典，以便得到:

I want to convert it to a dictionary so that I get:

red     d
yellow  c
blue    b

如果数据集很大，那么请避免使用任何迭代方法.我还没有找到解决方案.感谢您的帮助.

The dataset if quite large, so please avoid any iterative method. I haven't figured out a solution yet. Any help is appreciated.

推荐答案

首先，如果您确实希望将其转换为字典，则将所需的键值转换为索引的索引会更好一些.数据框:

First of all, if you really want to convert this to a dictionary, it's a little nicer to convert the value you want as a key into the index of the DataFrame:

df.set_index('a', inplace=True)

这看起来像:

        b  c  d
a              
red     0  0  1
yellow  0  1  0
blue    1  0  0

您的数据似乎是一次性"编码.首先，您必须使用此处详细介绍的方法:

Your data appears to be in "one-hot" encoding. You first have to reverse that, using the method detailed here:

series = df.idxmax(axis=1)

这看起来像:

a
red       d
yellow    c
blue      b
dtype: object

快到了！现在，使用 to_dict 在值"列上(这是将列a设置为索引的地方):

Almost there! Now and use to_dict on the 'value' column (this is where setting column a as the index helps out):

series.to_dict()

这看起来像:

{'blue': 'b', 'red': 'd', 'yellow': 'c'}

我想这就是您要寻找的.作为单线:

Which I think is what you are looking for. As a one-liner:

df.set_index('a').idxmax(axis=1).to_dict()

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