Pandas combining sparse columns in dataframe

Question

I am using Python, Pandas for data analysis. I have sparsely distributed data in different columns like following

| id | col1a | col1b | col2a | col2b | col3a         


        

Answer 1

You can use df.stack() assuming 'id' is your index else set 'id' as index. Then use pd.pivot_table.

df = df.stack().reset_index(name='val',level=1)
df['group'] = 'g'+ df['level_1'].str.extract('col(\d+)')
df['level_1'] = df['level_1'].str.replace('col(\d+)','')
df.pivot_table(index=['id','group'],columns='level_1',values='val')

level_1    cola  colb
id group
1  g1      11.0  12.0
2  g2      21.0  86.0
3  g1      22.0  87.0
4  g3     545.0  32.0