write a program to print and find sum of principal diagonal elements of matrix and also sum of secondary diagonal elements

Question

m=[[1,2,3],[4,5,6],[1,2,3]]
sum=0
for i in range (3):
for j in range (3):
if i=j:
sum=sum+m[i][j]
print(sum)

I wrote this for sum of principal diagonal elements but I am getting error message can u modify the code so that I get the desired result. thanks in advance

Answer 1

In if statement write

i == j

Hope this helps☺️☺️.

Answer 2

You could also do it with just one loop:

for i in range(3):
sum += m[i][i]

Also, since sum() is a built-in function, it may be better to use a different variable name. The term we use in mathematics for the sum of the principal diagonal elements is "trace"; you could use that 😉