Pandas - cumulative sum of two columns

[michalmonday]

Glad I could help, btw I think it would be important to make sure that the 'Year' value actually groups games from particular season, not strictly a year.

import pandas as pd

def get_team_names(df):
    return df[0][0], df[1][0]

df  = pd.DataFrame([
["Gothenburg", "Malmo", 2010,"A"],
["Malmo","Gothenburg",  2010, "D"],
["Malmo", "Gothenburg", 2010, "A"],
["Gothenburg", "Malmo", 2010, "H"],
["Gothenburg", "Malmo" ,2011, "D"],
["Gothenburg", "Malmo", 2011, "A"],
["Gothenburg", "Malmo", 2011, "H"],
["Malmo", "Gothenburg", 2011, "A"],
["Gothenburg", "Malmo", 2012, "H"],
["Malmo", "Gothenburg", 2012, "H"],
[ "Malmo","Gothenburg", 2012, "D"],
[ "Malmo", "Gothenburg",2012, "H"],
["Malmo", "Gothenburg", 2013, "H"],
[ "Malmo","Gothenburg", 2013, "D"],
[ "Malmo", "Gothenburg",2013, "H"],
 
])

team_1, team_2 = get_team_names(df)

df.columns = ['H_team', 'A_team', 'Year', 'Result']

df['H_points'] = 0
df['A_points'] = 0

for year in set(df['Year']):

    draws = (df['Result']=='D').where(df['Year'] == year)

    hh = (df['Result']=='H').where((df['H_team'] == team_1) & (df['Year'] == year)) * 3
    ha = (df['Result']=='A').where((df['A_team'] == team_1) & (df['Year'] == year)) * 3

    ah = (df['Result']=='H').where((df['H_team'] == team_2) & (df['Year'] == year)) * 3
    aa = (df['Result']=='A').where((df['A_team'] == team_2) & (df['Year'] == year)) * 3

    team_1_points = hh.add(ha, fill_value=0).add(draws, fill_value=0).cumsum().shift(1)
    team_2_points = ah.add(aa, fill_value=0).add(draws, fill_value=0).cumsum().shift(1)

    df['H_points'] = df['H_points'].add( team_1_points.where(df['H_team'] == team_1, team_2_points), fill_value=0)
    df['A_points'] = df['A_points'].add( team_1_points.where(df['A_team'] == team_1, team_2_points), fill_value=0)

    # set first game of season to 0 points - https://stackoverflow.com/a/37911231/4620679
    # otherwise it would be equal to the sum of points from previous season (due to ".shift(1)" method)
    df.loc[df.index[df['Year'] == year][:1], 'H_points'] = 0 
    df.loc[df.index[df['Year'] == year][:1], 'A_points'] = 0

print(df)

Output:
        H_team      A_team  Year Result  H_points  A_points
0   Gothenburg       Malmo  2010      A       0.0       0.0
1        Malmo  Gothenburg  2010      D       3.0       0.0
2        Malmo  Gothenburg  2010      A       4.0       1.0
3   Gothenburg       Malmo  2010      H       4.0       4.0
4   Gothenburg       Malmo  2011      D       0.0       0.0
5   Gothenburg       Malmo  2011      A       1.0       1.0
6   Gothenburg       Malmo  2011      H       1.0       4.0
7        Malmo  Gothenburg  2011      A       4.0       4.0
8   Gothenburg       Malmo  2012      H       0.0       0.0
9        Malmo  Gothenburg  2012      H       0.0       3.0
10       Malmo  Gothenburg  2012      D       3.0       3.0
11       Malmo  Gothenburg  2012      H       4.0       4.0
12       Malmo  Gothenburg  2013      H       0.0       0.0
13       Malmo  Gothenburg  2013      D       3.0       0.0
14       Malmo  Gothenburg  2013      H       4.0       1.0