How to get the summation of each of the 2 elements?

For example the list is:

stuff = [1, 2, 5, 7]

Now I created a new list named sum_list to store the summation of each of the 2 elements in stuff. The element in the sum_list will be 1+2, 1+5, 1+7, 2+5, 2+7, 5+7:

[3, 6, 8, 7, 9, 12]

>Solution :

You can do this in one hideous list comprehension:

[a + b for i, a in enumerate(my_list, start=1) for b in my_list[i:]]

Nested loops may be clearer:

result = []
for i, a in enumerate(my_list, start=1):
    for b in my_list[i:]:
        result.append(a + b)