arr = [12, 6, 8, 3, 10, 1, 0, 9]
a = list(zip(range(len(arr)), arr))
a.sort(key=lambda e: e[1], reverse=True)
print('\n'.join(f'{i} -> {x}' for i, x in a[:3]))
#初心者用
a = [12, 6, 8, 3, 10, 1, 0, 9]
below = min(a) - 1
for i in range(3):
mx = max(a)
i = a.index(mx)
print(f"{i} -> {mx}")
a[i] = below