迭代全局变量未触发 == 条件

Question

我尝试将turn = 0 放在play 函数中 我在 Stackoverflow 上阅读了几个类似的问题，并试图将 global turn 放在我的函数内部和外部。这些不会引发错误，但也不会导致转弯限制。为什么？有关如何解决此问题的任何想法？

我的直觉说，因为我已将变量 turn 设置为 global，所以我将继续引用 turn=0 的值，因为它是在函数之外设置的，但因为它会像你一样运行迭代数字轮流，我错了。

这是我的代码：

from random import randint

board = []

for x in range(5):
    board.append(["O"] * 5)

def print_board(board):
    for row in board:
        print " ".join(row)

print "Incredibly Simple Battleship!"
print_board(board)

def random_row(board):
    return randint(0, len(board) - 1)

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

ship_row = random_row(board)
ship_col = random_col(board)
print ship_row #erase after testing
print ship_col

global turn

def play(guess_row,guess_col):
  global turn
  if guess_row == ship_row and guess_col == ship_col:
    print "Congratulations! You sunk my battleship!"
  else:
    if turn == 4:
        print "Game Over"
    if guess_row not in range(5) or guess_col not in range(5):
        print "Oops, that's not even in the ocean."
    elif(board[guess_row][guess_col] == "X"):
        print "You guessed that one already."
    else:
        print "You missed my battleship!"
        board[guess_row][guess_col] = "X"
        print_board(board)
        print "Guess again:"
    print "Turn ",turn,":"
    guess_row = int(raw_input("Guess Row:"))
    guess_col = int(raw_input("Guess Col:"))
    turn += 1
    play(guess_row,guess_col)  


turn=0
guess_row = int(raw_input("Guess Row:"))
guess_col = int(raw_input("Guess Col:"))      
play(guess_row,guess_col)

这是我不使用全局时的原始错误：

Traceback (most recent call last):
 File "python", line 51, in <module>
 File "python", line 30, in play
UnboundLocalError: local variable 'turn' referenced before assignment

NB 我想接受不使用global 的建议，但还没有找到替代方案。

Answer 1

这是一个通过递归 play() 函数上的额外变量来跟踪转弯的版本。请注意，我还为您添加了一个回报，以便游戏可以在 Game Over 时结束。 :)

from random import randint

board = []

for x in range(5):
    board.append(["O"] * 5)

def print_board(board):
    for row in board:
        print " ".join(row)

print "Incredibly Simple Battleship!"
print_board(board)

def random_row(board):
    return randint(0, len(board) - 1)

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

ship_row = random_row(board)
ship_col = random_col(board)
print ship_row #erase after testing
print ship_col


def play(guess_row,guess_col, turn):
  if guess_row == ship_row and guess_col == ship_col:
    print "Congratulations! You sunk my battleship!"
  else:
    if turn == 4:
        print "Game Over"
        return
    if guess_row not in range(5) or guess_col not in range(5):
        print "Oops, that's not even in the ocean."
    elif(board[guess_row][guess_col] == "X"):
        print "You guessed that one already."
    else:
        print "You missed my battleship!"
        board[guess_row][guess_col] = "X"
        print_board(board)
        print "Guess again:"
    print "Turn ",turn,":"
    guess_row = int(raw_input("Guess Row:"))
    guess_col = int(raw_input("Guess Col:"))
    play(guess_row,guess_col, turn + 1)


guess_row = int(raw_input("Guess Row:"))
guess_col = int(raw_input("Guess Col:"))
play(guess_row,guess_col, 0)