def split_list(lst, n):
for i in range(0, len(lst), n):
yield lst[i:i + n]
lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
result = list(split_list(lst, 3))
print(result)
'''
run:
[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], [13, 14, 15], [16, 17, 18], [19]]
'''