# matrix = [
# [1,2,3],
# [4,5,6],
# [7,8,9]
# ]
# print(matrix[2][1])
# matrix[2][1] = 20
# print(matrix[2][1])

# for row in matrix:
#     for item in row:
#         print(item)

#list methods 

# numbers = [5,2,1,5,7,4]
# print(numbers)
# #adds 20 to the end
# numbers.append(20)
# #adds 10 at the 0 index
# numbers.insert(0,10)
# #removes 2
# numbers.remove(2)
# #Returns true or false if number is present in list
# print(7 in numbers)
# #returns how many times 5 occurs 
# print(numbers.count(5))
# print(numbers)
# #deletes values in list
# numbers.sort()
# print(numbers)