make a dataframe base on a rows and columns of another dataframe

Question

i have a a dataframe 'a' like this:

A header	c1	c2	c3	c4	c5
c1	0	1	3	4	2
c2	2	4	3	2	4
c3	2	4	1	2	2
c4	8	4	6	5	7
c5	7	4	5	8	9

now, i want to make a dataframe based on previous dataframe with name 'b'.

column1	column2	column3
c1	c1	0
c1	c2	1
c1	c3	3
c1	c4	4
c1	c5	2
c2	c1	2
c2	c2	4
c2	c3	3
c2	c4	2
c2	c5	4
c3	c1	2
c3	c2	4
c3	c3	1
c3	c4	2
c3	c5	2
c4	c1	8
c4	c2	4
c4	c3	6
c4	c4	5
c4	c5	7
c5	c1	7
c5	c2	4
c5	c3	5
c5	c4	8
c5	c5	9

could you help me to make this second dataframe ? thanks

Answer 1

You can try this:

a.stack().reset_index()

Answer 2

You can use the .melt function as follow:

pd.melt(df1, id_vars=['A header'], value_vars=['c1', 'c2','c3','c4','c5'])

you can check the documentation here : https://pandas.pydata.org/docs/reference/api/pandas.melt.html