list1 = [1, 2, 3, 4, 5, 6, 1, 2, 3]

print(list1.count(2))    # count the appearance of element 2 in the list

print(list1.count(100))  # count the appearance of element 100 in the list

print(list1.count(1))  # count the appearance of element 1 in the list