Python: Converting multiple columns to a single column with categorical data

Question

If I have this table:

City	State	Person 1	Person 2
Atlanta	GA	Bob	Fred

But, I want to convert it to:

City	State	Person#	Person Name
Atlanta	GA	1	Bob
Atlanta	GA	2	Fred

What is the most efficient way to accomplish this?

user_15239951 · Answer

Use melt:

out = df.melt(['City', 'State'], var_name='Person#', value_name='Person Name')
out['Person#'] = out['Person#'].str.extract('(\d+)')

>>> out
       City State Person# Person Name
0  Atlanta    GA        1        Bob 
1  Atlanta    GA        2        Fred