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

There is a more efficient way to do these type of problems that involve melting multiple different sets of columns. pd.wide_to_long is built for these exact situations.

pd.wide_to_long(df, stubnames=['a', 'b', 'c'], i='id', j='dropme', sep='_')\
  .reset_index()\
  .drop('dropme', axis=1)\
  .sort_values('id')

    id  a  b   c
0  101  a  1  aa
2  101  b  2  bb
4  101  c  3  cc
1  102  d  4  dd
3  102  e  5  ee
5  102  f  6  ff