using .index(" ") for nested list in python

I want to get the index of the "4" in the nested list, it is working cause I suppress the error. any idea for a alternative?

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

for i in range(len(a)):
    try:
        index = a[i].index(4)
        print(i, index)  
    except:
        pass

>Solution :

This is code that won’t throw an error and doesn’t use index() function.

for i in range(len(a)):
    for j in range(len(a[i])):
        if a[i][j] == 4:
            print("Found at", i, j)
            break