pandas rearrange columns into rows

Question

i have a dataframe df which has 2 rows and 3 columns a,b,c like below :

   A     B     C     
0  1.1   1.2   1.3
1  3.1   3.5   3.9

Required output :I want like below without needing column headers

0  1.1
   1.2
   1.3
1  3.1
   3.5
   3.9

Answer 1

Let's first create the dataframe that OP is using

import pandas as pd

df = pd.DataFrame(data=[[1.1, 1.2, 1.3], [3.1, 3.5, 3.9]], columns=['A', 'B', 'C'])

Now, in order to convert the columns into rows, this has a special name "transposition", and one can use dataframe.transpose as follows

df = df.transpose()

or dataframe.T (T is an accessor for the transpose method)

df = df.T

The final result is

print(df)

[Out]:
     0    1
A  1.1  3.1
B  1.2  3.5
C  1.3  3.9

Given this new requirement that OP mentioned, if one wants to concat the second column under the first column, the following will do the work

df = df[0].append(df[1]).reset_index(drop=True)

print(df)

[Out]:
0    1.1
1    1.2
2    1.3
3    3.1
4    3.5
5    3.9