How to reverse the index value in Python using for loop with a given list

Question

I want to create a function that prints out a tic-tac-toe board with a given list that position its index value on the board in a reverse order like on a number keyboard that is from 9 to 1, with the 1st row having the index value of 7, 8, 9: 2nd row 4, 5, 6: 3rd row 1, 2, 3.

For example: a given list

test_board = ['O','O','X','X','X','O','X','O','X']

That show print out like this:

 X | O | X 
---|---|---
 X | X | O 
---|---|---
 O | O | X  

I wrote this function:

def display_board(board):

    h_sep = '-' * 3
    for i in range(3):

        for j in reversed(board[1:]):

            print(f"{j:^3}|{j:^3}|{j:^3}")

        if i != 2:
            print(f"{h_sep:^3}|{h_sep:^3}|{h_sep:^3}")

But i get this print out when i call the function with the given list:

test_board = ['O','O','X','X','X','O','X','O','X']
display_board(test_board)

Output:

 X | X | X 
 O | O | O 
 X | X | X 
 O | O | O 
 X | X | X 
 X | X | X 
 X | X | X 
 O | O | O 
---|---|---
 X | X | X 
 O | O | O 
 X | X | X 
 O | O | O 
 X | X | X 
 X | X | X 
 X | X | X 
 O | O | O 
---|---|---
 X | X | X 
 O | O | O 
 X | X | X 
 O | O | O 
 X | X | X 
 X | X | X 
 X | X | X 
 O | O | O 

Edited: Can i use for loop to achieve this without writing multiple print statement like this:

print(f"{board[6]:^3}|{board[7]:^3}|{board[8]:^3}")
print(f"{h_sep:^3}|{h_sep:^3}|{h_sep:^3}")
print(f"{board[3]:^3}|{board[4]:^3}|{board[5]:^3}")
print(f"{h_sep:^3}|{h_sep:^3}|{h_sep:^3}")
print(f"{board[0]:^3}|{board[1]:^3}|{board[2]:^3}")

Answer 1

In your second for you are printing it 3 times before going to the next line.

Your function with the following modifications would work for your problem:

def display_board(board):
h_sep = '-' * 3
for i in reversed(range(3)):

    print(f"{board[i*3]:^3}|{board[i*3+1]:^3}|{board[i*3+2]:^3}")

    if i != 0:
        print(f"{h_sep:^3}|{h_sep:^3}|{h_sep:^3}")

Answer 2

You can use an iter to achieve this.

Solution

def display_board(board):
    h_sep = '-' * 3
    it = iter(reversed(board))
    count = 0
    for j in it:
        print(f"{j:^3}|{next(it):^3}|{next(it):^3}")
        if count < 2: 
            print(f"{h_sep:^3}|{h_sep:^3}|{h_sep:^3}")
            count+=1

test_board = ['X','O','O','O','X','X','X','O','X']
display_board(test_board)

Just to visualize the result, I used numbers in your test_board :

def display_board(board):
    h_sep = '-' * 3
    it = iter(reversed(board))
    for j in it:
        print(f"{int(j)-2:^3}|{int(next(it)):^3}|{int(next(it))+2:^3}")
        if int(j) > 3: print(f"{h_sep:^3}|{h_sep:^3}|{h_sep:^3}")

test_board = ['1','2','3','4','5','6','7','8','9']
display_board(test_board)

OUT:

 7 | 8 | 9 
---|---|---
 4 | 5 | 6
---|---|---
 1 | 2 | 3

Answer 3

You can use join to insert the vertical lines and then loop in reverse order.

test_board = ['O','O','X','X','X','O','X','O','X']

for i in range(3,-1,-1):
    li=test_board[i*3:(i+1)*3]
    print('|'.join(li))
    if 0<i<3: print('-'*5)

Answer 4

a longer version of the solution that can handle size of board greater than 3

    def display_board(board, size=3):
        parts = []
        h_seps = []
        for i in range(size):
            begin = i * size
            end = begin + size
            parts.append(board[begin:end])
            h_seps.append("-" * 3)

        first = True
        while len(parts) > 0:
            part = parts.pop()

            if first is False:
                print("|".join(h_seps))

            first = False
            print(" " + " | ".join(part))

    display_board(["O", "O", "X", "X", "X", "O", "X", "O", "X"])

Answer 5

If you want pythonic-one-liner, then here you go

def display_board(board):
    def display_board(board):
        for i in range(3,-1,-1): print(' | '.join(board[i*3:(i+1)*3]),'\n--|---|---' if 0 < i < 3 else '' )

test_board = ['1','2','3','4','5','6','7','8','9']
display_board(test_board)