Perfect numbers X62099

A proper divisor of a number is a positive factor of that number other than the number itself. For example, the proper divisors of 6 are 1, 2, and 3. A perfect number is a positive integer that is equal to the sum of its proper positive divisors. For instance, 6 = 1 + 2 + 3 and 28 = 1 + 2 + 4 + 7 + 14 are perfect numbers. In contrast, 1, 2, 3 and 18 are not perfect.

Write a function show_perfect(f) that given a list f of integers greater than zero computes the first perfect number that appears in f, if any. When f has no perfect numbers the function returns −1.

The following function proper_divisors(n) that computes the ordered list of proper divisors of a natural number n can be helpful.

def proper_divisors(n):
    '''
    n is an integer greater than zero
    returns the ordered list of proper divsisors of n
    >>> proper_divisors(6)
    [1, 2, 3]
    >>> proper_divisors(284)
    [1, 2, 4, 71, 142]
    >>> proper_divisors(1)
    []
    '''
    if n == 1:
        return []
    result = [1]
    d = 2
    while d*d <= n:
        if n%d == 0:
            result.append(d)
            if n//d != d:
                result.append(n//d)
        d += 1
    return sorted(result)