Pandas - Convert columns to new rows after groupby

问题

I have a pandas dataframe. I need to convert some of the columns into rows. The dataframe has same data in the first two columns for every 3 rows. So, I need 6 more columns as you will see in my expected dataframe. I have the following dataframe:

shopCode    Product   Code  Score
    111      Apple    123    0.70
    111      Apple    456    0.75
    111      Apple    789    0.80
    222      Orange   142    0.66
    222      Orange   136    0.83
    222      Orange   623    0.76

My expected dataframe is:

shopCode  Product   Code1 Code2 Code3 Score1 Score2 Score3
  111      Apple     123   456   789   0.70   0.75   0.80
  222      Orange    142   136   623   0.66   0.83   0.76

I tried to use df.pivot(index=['shopCode', 'Product'], columns=['Code1', 'Code2', 'Code3', 'Score1', 'Score2', 'Score3'], values=['Code', 'Score']) but it doesn't work.

回答1:

We using pivot_table

df=pd.pivot_table(df,index=['shopCode','Product'],columns=df.groupby(['shopCode','Product']).cumcount().add(1),values=['Code','Score'],aggfunc='sum')
df.columns=df.columns.map('{0[0]}{0[1]}'.format) 
df
Out[112]: 
                  Code1  Code2  Code3  Score1  Score2  Score3
shopCode Product                                             
111      Apple      123    456    789    0.70    0.75    0.80
222      Orange     142    136    623    0.66    0.83    0.76

After reset_index

df.reset_index()
Out[113]: 
   shopCode Product  Code1  Code2  Code3  Score1  Score2  Score3
0       111   Apple    123    456    789    0.70    0.75    0.80
1       222  Orange    142    136    623    0.66    0.83    0.76

回答2:

Can be achieved with pandas groupby and dictionary merge.

df.groupby(['shopCode', 'Product']).apply(lambda x: pd.Series(
                               {
                                **{'Code'+str(i+1): t for i,t in enumerate(x.Code)},
                                **{'Score'+str(i+1): t for i,t in enumerate(x.Score)}
                               }
                             )).reset_index()

来源：https://stackoverflow.com/questions/47849364/pandas-convert-columns-to-new-rows-after-groupby

标签

python

pandas

group-by

pivot