Compute for last two elements from dataframe (Python)-CodePudding

I have the following pandas dataframe (df_merge),

    Date       Type Counter
0   2021-07-09  T1  1420.000
1   2021-07-09  T2  856.000
2   2021-07-09  T3  1010.000
3   2021-07-09  P   3.408
0   2021-11-30  T1  1775.000
1   2021-11-30  T2  1069.000
2   2021-11-30  T3  1210.000
3   2021-11-30  P   3.408

I want to compute division last two elements of T1 type. 1775.000 / 1420.000 = 1.25

I wrote this code but is there a simpler and shorter way to do this?

df_merge[df_merge['Type']=='T1'].reset_index()['Counter'][1] / df_merge[df_merge['Type']=='T1'].reset_index()['Counter'][0]

Thanks

CodePudding user response：

Filter column with condition in DataFrame.loc:

s = df_merge.loc[df_merge['Type']=='T1', 'Counter']
print (s)
0    1420.0
0    1775.0
Name: Counter, dtype: float64

And then select values by positions in Series.iat - last by -1 and last previous by -2:

out = s.iat[-1] / s.iat[-2]
print (out)
1.25

If need divide second by first:

out = s.iat[1] / s.iat[0]
print (out)
1.25