How to swap certain columns in pandas dataframe?

Question

I have a pandas dataframe like below

Descr id state 01/2012 02/2012 04/2012 05/2015 08/2018
aa     1 new    20      30      40     50      60

And, I want to change it as

DateRange Descr id state value
01/2012   aa     1 new   20
02/2012   aa     1 new   30
04/2012   aa     1 new   40
05/2015   aa     1 new   50
08/2018   aa     1 new   60

Answer 1

Use DataFrame.melt:

df = df.melt(['Descr','id','state'], var_name='DateRange')
#change order of columns if necessary
df = df[['DateRange','Descr','id','state','value']]
print (df)
  DateRange Descr  id state  value
0   01/2012    aa   1   new     20
1   02/2012    aa   1   new     30
2   04/2012    aa   1   new     40
3   05/2015    aa   1   new     50
4   08/2018    aa   1   new     60