pyFind2ndLargestInteger

# Return the 2nd largest integer element from a list (or the only element if only 1)
# Return 9900 if the list is empty, or contains any non-integer values
# Mike Kerry - 13-March-2021

def get_2nd_largest(inlist):
    if not inlist:
        return 9900         # List is empty, so return 9900
    try:
        v = sum(inlist)     # Try and compute the sum of all the list entries
    except:
        return 9900         # sum was not possible, therefore the list contained a non-integer or non-float
    if isinstance(v, float):
        return 9900         # The sum produced a float result, therefore the list contained at least one float value

    inlist.sort(reverse=True)       # Sort the list in reverse order
    inlist.append(inlist[-1])       # duplicate the smallest element
    return inlist[1]                # return the 2nd largest element

# Test data:
tests = [1,2,3,4], [6, 8, 4, 4, 6], [53, 23], [13], \
        [12, "notnumber", 23], \
        [-11, -3, -15, -9, -16], [], [1, 2, 5.5]

for t in tests:
    print(t, get_2nd_largest(t.copy()))

# results:
# [1, 2, 3, 4] 3
# [6, 8, 4, 4, 6] 6
# [53, 23] 23
# [13] 13
# [12, 'notnumber', 23] 9900
# [-11, -3, -15, -9, -16] -9
# [] 9900
# [1, 2, 5.5] 9900