Pandas Melt several groups of columns into multiple target columns by name

Question

I would like to melt several groups of columns of a dataframe into multiple target columns. Similar to questions Python Pandas Melt Groups of Initial Columns Into Multiple T

Answer 1

cols = df.columns.difference(['id'])

pd.lreshape(df, cols.groupby(cols.str.split('_').str[0])).sort_values('id')
Out: 
    id  a   c  b
0  101  a  aa  1
2  101  b  bb  2
4  101  c  cc  3
1  102  d  dd  4
3  102  e  ee  5
5  102  f  ff  6