Using higher order functions to filter/sort/reduce nested dictionaries

Question

I have been given a class exercise to solve in Python and I have no idea how to go about it:

get_wins(wsu_games, team)
Assume you would like to find the scores for the games WSU won against a given team. Write a function get_wins that takes the WSU game data and a team name as input, and returns a list of tuples that includes the years and scores of each game WSU played and won against that team.

For example,
get_wins(wsu_games,'UTAH') returns [(2018, (28, 24))] (WSU played 4 games with 'UTAH' but won only the 2018 game)
get_wins(wsu_games,'STAN') returns [(2018, (41, 38)), (2019, (49, 22)), (2021, (34, 31))] (WSU played 3 games with 'STAN' and won all 3 games)

The dataset:

wsu_games = {
      2018: { "WYO":(41,19), "SJSU":(31,0), "EWU":(59,24), "USC":(36,39), "UTAH":(28,24), 
              "ORST":(56,37), "ORE":(34,20), "STAN":(41,38), "CAL":(19,13), "COLO":(31,7), 
              "ARIZ":(69,28), "WASH":(15,28), "ISU":(28,26)},
      2019: { "NMSU":(58,7), "UNCO":(59,17), "HOU":(31,24), "UCLA":(63,67), "UTAH":(13,38), 
              "ASU":(34,38), "COLO":(41,10), "ORE":(35,37), "CAL":(20,33), "STAN":(49,22), 
              "ORST":(54,53), "WASH":(13,31), "AFA":(21,31) },
      2020: { "ORST":(38,28), "ORE":(29,43), "USC":(13,38), "UTAH":(28,45)},
      2021: { "USU":(23,26), "PORT ST.":(44,24), "USC":(14,45), "UTAH":(13,24), "CAL":(21,6),
              "ORST":(31,24), "STAN":(34,31), "BYU":(19,21), "ASU":(34,21), "ORE":(24,38), 
              "ARIZ":(44,18), "WASH":(40,13), "CMU":(21,24)} }

We are not allowed to use loops of any kind to solve problems in this class. (Solving with loops would be relatively easy, higher order functions not so much).

How can I do this?

Answer 1

Try:

def get_wins(games, team):
    return list(
        map(
            lambda v: (v, games[v][team]),
            filter(
                lambda k: team in games[k]
                and games[k][team][0] > games[k][team][1],
                games,
            ),
        )
    )


print(get_wins(wsu_games, "STAN"))

Prints:

[(2018, (41, 38)), (2019, (49, 22)), (2021, (34, 31))]