def print_board() -> None:
    """ Prints the board """

    length = 3 * (SIZE - 1) + SIZE + 4

    print()

    print('-' * length)

    for row in board:
        print('| ' + ' | '.join(row) + ' |')
        print('-' * length)

    print()

def isValid(row: int, col: int) -> bool:
    """ Returns if a cell index is valid """

    return 0 <= row < SIZE and 0 <= col < SIZE

def isSafe(row: int, col: int) -> bool:
    """ Checks if the given index position is safe """

    # Checks if the column is safe
    for i in range(SIZE):
        if i != row and board[i][col] != ' ':
            return False

    # Checks if the row is safe
    for j in range(SIZE):
        if j != col and board[row][j] != ' ':
            return False

    # Checks if the diagonals are safe
    for k in range(min(SIZE, SIZE)):
        if isValid(row + k, col + k) and board[row + k][col + k] != ' ' or \
           isValid(row - k, col + k) and board[row - k][col + k] != ' ' or \
           isValid(row + k, col - k) and board[row + k][col - k] != ' ' or \
           isValid(row - k, col - k) and board[row - k][col - k] != ' ':

            return False

    return True


def backtrack(row=0, total=0) -> bool:
    """ Backtracks and fills chacks for every possible combination """

    # If all rows are safely filled with queens
    if row == SIZE:
        # print_board()  # Uncomment the code to print the current solution
        # input('Enter to continue... ')

        return 1

    for col in range(SIZE):
        # If the current index is safe, check for the next row
        if isSafe(row, col):
            board[row][col] = 'Q'

            total += backtrack(row + 1)

            board[row][col] = ' '

    return total


def solve() -> None:
    """ Calls backtrack and prints number of solutions """

    total = backtrack()

    print()

    if not total:
        print('No possible solution was found')
    elif total == 1:
        print('There is a total of 1 solution')
    else:
        print(f'There are a total of {total} solutions')


if __name__ == '__main__':
    SIZE = int(input('Enter the size of the board: '))

    board = [[' '] * SIZE for row in range(SIZE)]

    solve()

def print_board() -> None:
    """ Prints the board """

    length = 3 * (SIZE - 1) + SIZE + 4

    print()

    print('-' * length)

    for row in board:
        print('| ' + ' | '.join(row) + ' |')
        print('-' * length)

    print()

def isValid(row: int, col: int) -> bool:
    """ Returns if a cell index is valid """

    return 0 <= row < SIZE and 0 <= col < SIZE

def isSafe(row: int, col: int) -> bool:
    """ Checks if the given index position is safe """

    # Checks if the column is safe
    for i in range(SIZE):
        if i != row and board[i][col] != ' ':
            return False

    # Checks if the row is safe
    for j in range(SIZE):
        if j != col and board[row][j] != ' ':
            return False

    # Checks if the diagonals are safe
    for k in range(SIZE):
        if isValid(row + k, col + k) and board[row + k][col + k] != ' ' or \
           isValid(row - k, col + k) and board[row - k][col + k] != ' ' or \
           isValid(row + k, col - k) and board[row + k][col - k] != ' ' or \
           isValid(row - k, col - k) and board[row - k][col - k] != ' ':

            return False

    return True


def backtrack(row=0, total=0) -> bool:
    """ Backtracks and fills chacks for every possible combination """

    # If all rows are safely filled with queens
    if row == SIZE:
        # print_board()  # Uncomment the code to print the current solution
        # input('Enter to continue... ')

        return 1

    for col in range(SIZE):
        # If the current index is safe, check for the next row
        if isSafe(row, col):
            board[row][col] = 'Q'

            total += backtrack(row + 1)

            board[row][col] = ' '

    return total


def solve() -> None:
    """ Calls backtrack and prints number of solutions """

    total = backtrack()

    print()

    if not total:
        print('No possible solution was found')
    elif total == 1:
        print('There is a total of 1 solution')
    else:
        print(f'There are a total of {total} solutions')


if __name__ == '__main__':
    SIZE = int(input('Enter the size of the board: '))

    board = [[' '] * SIZE for row in range(SIZE)]

    solve()

Though it does work, I'm not satisfied. I want to make this code as short as possible while also following Pep8 rules.

Though it does work, I'm not satisfied yet. 

I want to make this code as short as possible while also following Pep8 rules.