python list语法学习（带例子）

from random import randint
def creat_board(length):
    board = []
    for i in range(length):
        board.append(['O'] * length)
    return board
def print_board(x):
    for row in x:
        print " ".join(row)
def random_row(board):
    return randint(0, len(board) - 1)

def random_col(board):
    return randint(0,len(board[0]) - 1)

length = int(raw_input("Enter board's length you:"))
board = creat_board(length)
print_board(board)
turns = int(raw_input("Enter turns you want to play:"))
for turn in range(turns):
    ship_row = random_row(board)
    ship_col = random_col(board)
    print "This is " + str(turn + 1) + "th time to guess:"
    guess_row = int(raw_input("Enter the row you guess:"))
    guess_col = int(raw_input("Enter the col you guess:"))

    if guess_row == ship_row and guess_col == ship_col:
        print "You win!"
        break
    else:
        if (guess_row len(board) - 1) or (guess_col len(board) - 1):
            print "Incorrect input!"
            if turn == turns - 1:
                print "Turns out!"
        elif board[guess_row][guess_col] == 'X':
            print "You have guessed it already!"
            if turn == turns - 1:
                print "Turns out!"
        else:
            print "You guess wrong!"
            board[guess_row][guess_col] = 'X'
            print_board(board)
            if turn == turns - 1:
                print "Turns out!"

曾经犯的错误：
1.创建board函数忘记返回一个board，所以它一直为空，导致后面的操作都越界了；
2.生成随机位置的时候，位置row和col的命名一直是跟生成的函数名一样（random_row=random_row(board)），导致TypeError: 'int' object is not callable错误。