Method 1:

This project adds two matrices together.  They must be the same dimensions.  Method 1 uses nested for statements.

X = [[1,2,3],
[4 ,5,6],
[7 ,8,9]]

Y = [[9,8,7],
[6,5,4],
[3,2,1]]

result = [[0,0,0],
[0,0,0],
[0,0,0]]

# iterate through rows
for i in range(len(X)):
# iterate through columns
for j in range(len(X[0])):
result[i][j] = X[i][j] + Y[i][j]

for r in result:
print(r)
[10, 10, 10]
[10, 10, 10]
[10, 10, 10]

Method 2:
This combines the output with the nested for loops

X = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]

Y = [[9, 8, 7],
[6, 5, 4],
[3, 2, 1]]

answer = [[X[i][j] + Y[i][j] for j in range(len(X[0]))] for i in range(len(X))]

for r in answer:
print(r)
[10, 10, 10]
[10, 10, 10]
[10, 10, 10]