while len(outerlist) <= idx:
outerlist.append([])
board = []
for i in range(6): # create a list with nested lists
board.append([])
for n in range(6):
board[i].append("O") # fills nested lists with data
board = []
for i in range(6): # create a list with nested lists
board.append([])
for n in range(6):
board[i].append("O") # fills nested lists with data
# it appends a list into a list
list1 = [1,2,3,4,5]
list1.append([6,7])
# ouput = [1, 2, 3, 4, 5, [6, 7]]