TwoSum.py

def main():
    """
    This program allows to identify position of two numbers in a given
    list that when added together fulfills the target sum 
    e.g. input numbers 2, 7, 8, 9 and 
    for target sum 15 expected result is 1 , 2 
    for target sum 17 expected result is 2 , 3
    T(n) = O(n)
    """
    #accept user input for the list of numbers
    input_nums = input("Enter comma separated list of numbers: ")
    num = eval(input_nums)

    #accept user input for the target sum
    input_target = input("Enter target sum: ")
    target = int(input_target)

    #define empty dictionary object
    dic = {}

    #loop through each number, subtract target with indexed num 
    # to identify other num to complete the target sum
    for i in range(0, len(num)):
        if dic.get(target-num[i]) == None:
            dic.update({num[i] : i})
        else:
            print(dic.get(target-num[i]), ',', i)
            break
        
if __name__ == "__main__":
    main()