import pandas as pd

df = pd.DataFrame({'A':['foo','foo','bar','bar'],
                   'B':['one','one','two','two'],
                   'C':[1,2,3,4]})
print(df)

     A    B  C
0  foo  one  1
1  foo  one  2
2  bar  two  3
3  bar  two  4

df_new = pd.melt(df, id_vars=['A'], var_name='new_col', value_name='new_val')
print(df_new)

     A new_col  new_val
0  foo       B      one
1  foo       B      one
2  bar       B      two
3  bar       B      two
4  foo       C        1
5  foo       C        2
6  bar       C        3
7  bar       C        4

import pandas as pd

data = {'Date':['2010-01-01', '2010-01-01', '2010-01-02', '2010-01-02'],
        'Region':['East', 'West', 'East', 'West'],
        'Sales':[100, 200, 300, 400],
        'Expenses':[50, 70, 90, 110]}
df = pd.DataFrame(data)

pivot = df.pivot_table(values=['Sales', 'Expenses'], index='Date', columns='Region')
print(pivot)

           Expenses       Sales     
Region         East West  East West
Date                               
2010-01-01       50   70   100  200
2010-01-02       90  110   300  400

melted = pd.melt(pivot.reset_index(), id_vars=['Date'], value_name='new')
melted['Region'] = melted['Region'].apply(lambda x: x[1])

new_pivot = melted.pivot_table(values='new', index='Date', columns='Region')
print(new_pivot)

Region      East  West
Date                 
2010-01-01   100   200
2010-01-02   300   400