pandas.DataFrame.stack

DataFrame.stack(level=-1, dropna=True)

Pivot a level of the (possibly hierarchical) column labels, returning a DataFrame (or Series in the case of an object with a single level of column labels) having a hierarchical index with a new inner-most level of row labels.

level : int, string, or list of these, default last level

Level(s) to stack, can pass level name

dropna : boolean, default True

Whether to drop rows in the resulting Frame/Series with no valid values

>>> s
     a   b
one  1.  2.
two  3.  4.

>>> s.stack()
one a    1
    b    2
two a    3
    b    4

stacked : DataFrame or Series