love dares you to

#1

def sorted_by_sum(pairs):
    a = pairs
    a.sort(key=sum, reverse=True)
    return a

print(sorted_by_sum([(1,2), (2,3), (3,4)]))

#2

def series(n):
    a = []
    if n>1:
        a = [1/i**4 for i in range(2, n)]

    return 1/1**4 - sum(a) + 1/n**4 - 1/n**4

import math

test = 7*(math.pi**4)/720
print(test - series(5))
print(test - series(10000))

#3

def compose(d1, d2):
    d = {}

    for k in d1.keys():
        val = d2.get(d1[k], None)
        if val != None:
            d[k] = val

    return d

print(compose({'a': 'A', 'b': 'B', 'c': 'C'}, {'B': 'BB', 'C': 'CC', 'D': 'DD'}))