Working with multidimensional lists?

Question

Python

Good afternoon. How to set a condition for a multidimensional list? For example, add all elements with index 1, provided that the zero elements are the same.
For example T =[[1,1],[1,2],[2,2],[2,4],[1,5],[1,6]]
Just started learning the language. I can not describe the condition of equality of zero elements.

Answer 1

from collections import defaultdict

t = [[1, 1], [1, 2], [2, 2], [2, 4], [1, 5], [1, 6]]

d = defaultdict(int)

for item in t:
    d[item[0]] += item[1]

print(d)

OUT

defaultdict(<class 'int'>, {1: 14, 2: 6})

Process finished with exit code 0