# How Voting Systems Work 5, Exercise 1: plurality, Borda and Dowdall for a five-candidate club vote
# 25 members rank five candidates (assumed, invented numbers).
# Print each method's scores and winner, and say whether the three agree.
from collections import Counter

groups = [
    (8, ("Eve", "Dan", "Cy", "Bo", "Ana")),
    (6, ("Ana", "Bo", "Cy", "Dan", "Eve")),
    (5, ("Cy", "Bo", "Dan", "Ana", "Eve")),
    (4, ("Bo", "Cy", "Ana", "Dan", "Eve")),
    (2, ("Dan", "Cy", "Bo", "Eve", "Ana")),
]
ballots = [r for count, r in groups for _ in range(count)]
k = len(ballots[0])

plural = Counter(b[0] for b in ballots)
borda, dowdall = Counter(), Counter()
for b in ballots:
    for place, c in enumerate(b):
        borda[c] += k - 1 - place
        dowdall[c] += 1 / (place + 1)

results = {}
for label, tally in (("plurality", plural), ("Borda", borda), ("Dowdall", dowdall)):
    tally = {c: round(tally[c], 2) for c in sorted(ballots[0])}
    results[label] = max(tally, key=tally.get)
    print(f"{label:<10}{tally} -> {results[label]}")
print("all three agree:", len(set(results.values())) == 1)

# Output when run:
# plurality {'Ana': 6, 'Bo': 4, 'Cy': 5, 'Dan': 2, 'Eve': 8} -> Eve
# Borda     {'Ana': 37, 'Bo': 61, 'Cy': 66, 'Dan': 52, 'Eve': 34} -> Cy
# Dowdall   {'Ana': 10.58, 'Bo': 12.17, 'Cy': 12.67, 'Dan': 10.17, 'Eve': 11.5} -> Cy
# all three agree: False