second_largest.py

"""
 Python program to find second largest value in a list, e.g., given

  [3, 2, 5, 2, 4]

find 4 and, possibly, its location (4).

Adapted from:
    www.geeksforgeeks.org/python-program-to-find-second-largest-number-in-a-list/
"""

def second_largest(list1):
    mx=max(list1[0],list1[1])
    secondmax=min(list1[0],list1[1])
    n =len(list1)
    for i in range(2,n):
        if list1[i]>mx:
            secondmax=mx
            mx=list1[i]
        elif list1[i]>secondmax and mx != list1[i]:
            secondmax=list1[i]
        else:
            if secondmax == mx:
                secondmax = list1[i]
    return secondmax


if __name__ == "__main__":

    # list of numbers - length of list should be at least 2
    list1 = [10, 20, 4, 45, 99]
    secondmax = second_largest(list1)
    print("Second highest number is : ",str(secondmax))