I need to make a small program that will take a 4x4 matrix and add the diagonal of the of the columns and rows.

```
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
```

Like this would add 1+2+3+4.

Sorry for being vague, this is what I came up with for adding a matrix by each column straight down. I also have not been using numpy yet.

```
matrix = [1,2,3,4],[5,6,7,8],[9,10,11,12] #Assume a list is given
total = 0
for column in range(0, len(matrix[0])):
for row in range(0, len(matrix)):
total += matrix[row][column]
print("Sum for column " + str(column) + " is " + str(total))
total = 0 #Reset total to zero before restarting count
```

I'm not 100% where to start with this so any ideas would be great. My teacher told us *offset* as a hint.

The diagonal elements are at the same row-column coordinates:

```
matrix = [[1,2,3,4],
[1,2,3,4],
[1,2,3,4],
[1,2,3,4]]
answer = sum(matrix[i][i] for i in range(len(matrix)))
```