Find all items with the top 5 unique values based upon 2nd element in tuple list

Question

I want to find the all tuple items with the top 5 max values in a tuple list based upon the 2nd element of the tuple. For example, I have a tuple list

x1 = [(a, 5), (b, 5), (c, 4), (d, 3), (e, 8), (f, 9), (g, 2), (h, 1)]

I want to get the following list:

x2 = [(a, 5), (b, 5), (c, 4), (d, 3), (e, 8), (f, 9)]

As the top 5 unique values for 2nd elements are 9, 8, 5, 4, 3 and a, b both have value 5, they both should be included in the list.

Any idea on how to realize this? Thanks!

Answer 1

Find the top 5 second elements:

i = set(list({x[1] for x in x1})[-5:])

Filter the list:

x2 = list(filter(lambda x: x[1] in i, x1))

Or even better:

ss = {x[1] for x in x1}
if len(ss) > 5:
    i = list(ss)[-5]
    x2 = list(filter(lambda x: x[1] >= i, x1))
else:
    x2 = x1

Output:

[('a', 5), ('b', 5), ('c', 4), ('d', 3), ('e', 8), ('f', 9)]

Answer 2

x1 = [('f', 9), ('e', 8), ('a', 5), ('b', 5), ('c', 4), ('d', 3), ('g', 2), ('h', 1)]
x1.sort(key=lambda x: x[1], reverse=True)
max5set = set()
i = 0
for _, num in x1:
    max5set.add(num)
    i += 1
    if (len(max5set) == 6):
        break
print(x1[:i-1])

output:

[('f', 9), ('e', 8), ('a', 5), ('b', 5), ('c', 4), ('d', 3)]

if you want to get this tuple list alphabetically, do

print(sorted(x1[:i-1], key=lambda x: x[0]))

output will be

[('a', 5), ('b', 5), ('c', 4), ('d', 3), ('e', 8), ('f', 9)]