请编写一段代码，实现简单的五子棋游戏

以下是一个简单的五子棋游戏代码示例：

import numpy as np

# 定义棋盘大小
board_size = 15

# 初始化棋盘
board = np.zeros((board_size, board_size))

# 定义落子函数
def play(board, row, col, player):
    board[row][col] = player
    
# 定义判断胜负函数
def is_win(board, player):
    # 判断行
    for i in range(board_size):
        for j in range(board_size-4):
            if board[i][j] == player and board[i][j+1] == player and board[i][j+2] == player and board[i][j+3] == player and board[i][j+4] == player:
                return True
    # 判断列
    for i in range(board_size-4):
        for j in range(board_size):
            if board[i][j] == player and board[i+1][j] == player and board[i+2][j] == player and board[i+3][j] == player and board[i+4][j] == player:
                return True
    # 判断对角线
    for i in range(board_size-4):
        for j in range(board_size-4):
            if board[i][j] == player and board[i+1][j+1] == player and board[i+2][j+2] == player and board[i+3][j+3] == player and board[i+4][j+4] == player:
                return True
    # 判断反对角线
    for i in range(board_size-4):
        for j in range(4, board_size):
            if board[i][j] == player and board[i+1][j-1] == player and board[i+2][j-2] == player and board[i+3][j-3] == player and board[i+4][j-4] == player:
                return True
    return False

# 定义两个玩家
player1 = 1
player2 = 2

# 开始游戏
while True:
    # 玩家1落子
    row, col = map(int, input("Player 1's turn: ").split())
    play(board, row, col, player1)
    if is_win(board, player1):
        print("Player 1 wins!")
        break
    # 玩家2落子
    row, col = map(int, input("Player 2's turn: ").split())
    play(board, row, col, player2)
    if is_win(board, player2):
        print("Player 2 wins!")
        break

在这个示例中，我们使用了numpy库来创建一个二维数组作为棋盘。落子函数play接受一个二维数组board、落子的行列坐标和玩家编号，将玩家的棋子标记在对应位置。判断胜负函数is_win则遍历棋盘，判断是否存在五个相同的棋子连成一线。最后使用while循环轮流让两个玩家落子，直到有一方胜利。