District Concordance- adding some rows year-wise

Question

I am trying to concord districts using my panel dataset for 12 years. some districts are newly carved out of older districts. For, example, a new district Agar Malwa was formed from the district Shajapur in 2014. I want to add Agar Malwa to Shajapur everytime it appears after 2014 and get only new combined Shajapur in my data set dropping Agar Malwa and Shajapur from it.

My dataset looks like following-

Year	District	State	values
2012	Shajapur	x	23
2013	Shajapur	x	21
2014	Shajapur	x	16
2014	Agar Malwa	x	8
2015	Shajapur	x	17
2015	Agar Malwa	x	10

upto year 2021. I need the new dataset in the following manner-

Year	District	State	values
2012	Shajapur	x	23
2013	Shajapur	x	21
2014	Shajapur	x	24
2015	Shajapur	x	27

up to year 2021. I have to do this for about 100 districts and which were formed, renamed, bifurcated between 2010 and 2021. Please suggest some loop code, or some basic code which can be used here.

Answer 1

    data = {'Year':['2012','2013','2014','2014','2015','2015'],
    'District': ['Shajapur','Shajapur','Shajapur','Agar Malwa','Shajapur','Agar Malwa'],
    'State':['x','x','x','x','x','x'], 'values':[23,21,16,8,17,10]}

df = pd.DataFrame(data)

df['District'].replace('Agar Malwa','Shajapur',inplace=True)

   Year  District State  values
0  2012  Shajapur     x      23
1  2013  Shajapur     x      21
2  2014  Shajapur     x      16
3  2014  Shajapur     x       8
4  2015  Shajapur     x      17
5  2015  Shajapur     x      10

df = df.groupby(['Year','District','State']).sum()

Year District State
2012 Shajapur x          23
2013 Shajapur x          21
2014 Shajapur x          24
2015 Shajapur x          27