用可能的最简单索引在python pandas中转置一列 [英] Transposing one column in python pandas with the simplest index possible

问题描述

我有以下数据(data_current):

import pandas as pd
import numpy as np

data_current=pd.DataFrame({'medicine':['green tea','fried tomatoes','meditation','meditation'],'disease':['acne','hypertension', 'cancer','lupus']})
data_current

我想做的是移置其中一列，这样，我不必为一列具有相同药物和不同疾病的药物排成一行，而为每种药物有一行并且有多个疾病列.保持索引尽可能简单也很重要，即0,1,2 ...，即我不想将'medicines'分配为索引列，因为我将其合并到其他键上. 因此，我需要获取data_needed

What I would like to do is to transpose one of the columns, so that instead of having multiple rows with same medicine and different diseases I have one row for each medicine with several columns for diseases. It is also important to keep index as simple as possible, i.e. 0,1,2... i.e. I don't want to assign 'medicines' as index column because I will merge it on some other key. So, I need to get data_needed

data_needed=pd.DataFrame({'medicine':['green tea','fried tomatoes','meditation'],'disease_1':['acne','hypertension','cancer'], 'disease_2':['np.nan','np.nan','lupus']})
data_needed

推荐答案

这里是实现输出的一种方法

Here's one to achieve the output

首先，在medicine上的groupby并获得disease作为列表

Firstly, groupby on medicine and get the disease as list

In [368]: md = (data_current.groupby('medicine')
                            .apply(lambda x: x['disease'].tolist())
                            .reset_index())

In [369]: md
Out[369]:
         medicine                0
0  fried tomatoes   [hypertension]
1       green tea           [acne]
2      meditation  [cancer, lupus]

然后将列中的列表转换为单独的列

Then convert the lists in column to separate columns

In [370]: dval = pd.DataFrame(md[0].tolist(), )

In [371]: dval
Out[371]:
              0      1
0  hypertension   None
1          acne   None
2        cancer  lupus

现在，您可以concat-md与dval

In [372]: md = md.drop(0, axis=1)

In [373]: data_final = pd.concat([md, dval], axis=1)

然后，根据需要重命名列.

And, rename the columns as you want.

In [374]: data_final.columns = ['medicine', 'disease_1', 'disease_2']

In [375]: data_final
Out[375]:
         medicine     disease_1 disease_2
0  fried tomatoes  hypertension      None
1       green tea          acne      None
2      meditation        cancer     lupus

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