Python - Summing elements on list of lists based on first element of inner lists

Question

I have a list

[[0.5, 2], [0.5, 5], [2, 3], [2, 6], [2, 0.6], [7, 1]]

I require the output from summing the second element in each sublist f

Answer 1

Will this work?

L = [[0.5, 2], [0.5, 5], [2, 3], [2, 6], [2, 0.6], [7, 1]]
nums = []
d = {}
for lst in L:
    if lst[0] not in d:
        d[lst[0]] = []
        nums.append(lst[0])
    d[lst[0]].append(lst[1])

for key in nums:
    print [key, sum(d[key])]

Output:

[0.5, 7]
[2, 9.6]
[7, 1]