Retrieve name of column from its Index in Pandas

I think you need index columns names by position (python counts from 0, so for fourth column need 3):

colname = df.columns[pos]

Sample:

df = pd.DataFrame({'A':[1,2,3],
                   'B':[4,5,6],
                   'C':[7,8,9],
                   'D':[1,3,5],
                   'E':[5,3,6],
                   'F':[7,4,3]})

print (df)
   A  B  C  D  E  F
0  1  4  7  1  5  7
1  2  5  8  3  3  4
2  3  6  9  5  6  3

pos = 3
colname = df.columns[pos]
print (colname)
D

pos = [3,5]
colname = df.columns[pos]
print (colname)
Index(['D', 'F'], dtype="object")