How to repeat a row for each value of its corresponding columns items

Question

col1	col2	col3
(str)1	(str)3	(str)34
(str)2	(str)4	(str)2

to

col1	col2
(str)1	(str)3
(str)1	(str)34
(str)2	(str)4
(str)2	(str)2

Answer 1

Try with melt then sort_values

out = df.melt('col1').sort_values('col1')#.drop('variable',1)
Out[426]: 
     col1 variable    value
0  (str)1     col2   (str)3
2  (str)1     col3  (str)34
1  (str)2     col2   (str)4
3  (str)2     col3   (str)2