python需要帮助，以了解在迭代过程中我的集合被更改的位置

Question

我为cs50任务建立了一个扫雷舰算法。我已识别出我的代码有问题。（扫雷艇类内）

该程序需要mineswipper.py和runner.py，并使用“python runner.py”执行

在使用python runner.py运行时，它会给我一个运行时错误：

Traceback (most recent call last):
  File "C:\Users\seng\Downloads\minesweeper\minesweeper\runner.py", line 220, in <module>
    ai.add_knowledge(move, nearby)
  File "C:\Users\seng\Downloads\minesweeper\minesweeper\minesweeper.py", line 230, in add_knowledge
    self.updateknowledge()
  File "C:\Users\seng\Downloads\minesweeper\minesweeper\minesweeper.py", line 274, in updateknowledge
    for safe in safes:
RuntimeError: Set changed size during iteration

这是代码。 扫雷舰

import itertools
import random
import copy

class Minesweeper():
    """
    Minesweeper game representation
    """

    def __init__(self, height=8, width=8, mines=8):

        # Set initial width, height, and number of mines
        self.height = height
        self.width = width
        self.mines = set()

        # Initialize an empty field with no mines
        self.board = []
        for i in range(self.height):
            row = []
            for j in range(self.width):
                row.append(False)
            self.board.append(row)

        # Add mines randomly
        while len(self.mines) != mines:
            i = random.randrange(height)
            j = random.randrange(width)
            if not self.board[i][j]:
                self.mines.add((i, j))
                self.board[i][j] = True

        # At first, player has found no mines
        self.mines_found = set()

    def print(self):
        """
        Prints a text-based representation
        of where mines are located.
        """
        for i in range(self.height):
            print("--" * self.width + "-")
            for j in range(self.width):
                if self.board[i][j]:
                    print("|X", end="")
                else:
                    print("| ", end="")
            print("|")
        print("--" * self.width + "-")

    def is_mine(self, cell):
        i, j = cell
        return self.board[i][j]

    def nearby_mines(self, cell):
        """
        Returns the number of mines that are
        within one row and column of a given cell,
        not including the cell itself.
        """

        # Keep count of nearby mines
        count = 0

        # Loop over all cells within one row and column
        for i in range(cell[0] - 1, cell[0] + 2):
            for j in range(cell[1] - 1, cell[1] + 2):

                # Ignore the cell itself
                if (i, j) == cell:
                    continue

                # Update count if cell in bounds and is mine
                if 0 <= i < self.height and 0 <= j < self.width:
                    if self.board[i][j]:
                        count += 1

        return count

    def won(self):
        """
        Checks if all mines have been flagged.
        """
        return self.mines_found == self.mines


class Sentence():
    """
    Logical statement about a Minesweeper game
    A sentence consists of a set of board cells,
    and a count of the number of those cells which are mines.
    """

    def __init__(self, cells, count):
        self.cells = set(cells)
        self.count = count

    def __eq__(self, other):
        return self.cells == other.cells and self.count == other.count

    def __str__(self):
        return f"{self.cells} = {self.count}"

    def known_mines(self):
        """
        Returns the set of all cells in self.cells known to be mines.
        """
        if len(self.cells) == self.count:
            return self.cells

    def known_safes(self):
        """
        Returns the set of all cells in self.cells known to be safe.
        """
        if 0 == self.count:
            return self.cells

    def mark_mine(self, cell):
        """
        Updates internal knowledge representation given the fact that
        a cell is known to be a mine.
        """
        if cell in self.cells:
            self.cells.remove(cell)
            self.count -= 1

    def mark_safe(self, cell):
        """
        Updates internal knowledge representation given the fact that
        a cell is known to be safe.
        """
        if cell in self.cells:
            self.cells.remove(cell)


class MinesweeperAI():
    """
    Minesweeper game player
    """

    def __init__(self, height=8, width=8):

        # Set initial height and width
        self.height = height
        self.width = width

        # Keep track of which cells have been clicked on
        self.moves_made = set()

        # Keep track of cells known to be safe or mines
        self.mines = set()
        self.safes = set()

        # List of sentences about the game known to be true
        self.knowledge = []

    def mark_mine(self, cell):
        """
        Marks a cell as a mine, and updates all knowledge
        to mark that cell as a mine as well.
        """
        self.mines.add(cell)
        for sentence in self.knowledge:
            sentence.mark_mine(cell)

    def mark_safe(self, cell):
        """
        Marks a cell as safe, and updates all knowledge
        to mark that cell as safe as well.
        """
        self.safes.add(cell)
        for sentence in self.knowledge:
            sentence.mark_safe(cell)

    def add_knowledge(self, cell, count):
        """
        Called when the Minesweeper board tells us, for a given
        safe cell, how many neighboring cells have mines in them.

        This function should:
            1) mark the cell as a move that has been made
            2) mark the cell as safe
            3) add a new sentence to the AI's knowledge base
               based on the value of `cell` and `count`
            4) mark any additional cells as safe or as mines
               if it can be concluded based on the AI's knowledge base
            5) add any new sentences to the AI's knowledge base
               if they can be inferred from existing knowledge
        """
        #1
        self.moves_made.add(cell)
        #2
        self.mark_safe(cell)
        #3
        i, j = cell
        removecell = []
        addcell = [(i-1, j-1), (i-1, j), (i-1, j+1), 
                (i, j-1), (i, j+1), 
                (i+1, j-1), (i+1, j), (i+1, j + 1),]
        for c in addcell:
            if c[0] < 0 or c[0] > 7 or c[1] < 0 or c[1] > 7:
                removecell.append(c)

        for c in removecell:
            addcell.remove(c)

        removecell = []
        for c in addcell:
            if c in self.mines:
                removecell.append(c)

        count -= len(removecell)
        for c in removecell:
            addcell.remove(c)

        removecell = []
        for c in addcell:
            if c in self.safes:
                removecell.append(c)

        for c in removecell:
            addcell.remove(c)

        #need filter for empty
        newsentence = Sentence(addcell, count)
        if len(newsentence.cells) > 0:
            self.knowledge.append(newsentence)
        print("dfs")

        self.updateknowledge()
        print("2")
        self.inference()
        print("3")


        

    def inference(self):
        for sentence1 in self.knowledge:
            for sentence2 in self.knowledge:
                if sentence1.cells.issubset(sentence2.cells):
                    new_cells = sentence2.cells - sentence1.cells
                    new_count = sentence2.count - sentence1.count
                    new_sentence = Sentence(new_cells, new_count)
                    if new_sentence not in self.knowledge:
                        self.knowledge.append(new_sentence)
                        self.updateknowledge()



    def updateknowledge(self):
        keepgoing = True
        while keepgoing:
            keepgoing = False
            for sentence in self.knowledge:

                mines = sentence.known_mines()
                if mines:
                    keepgoing = True
                    for mine in mines:
                        self.mark_mine(mine)

                safes = sentence.known_safes()
                if safes:
                    keepgoing = True
                    for safe in safes:
                        self.mark_safe(safe)


    def make_safe_move(self):
        """
        Returns a safe cell to choose on the Minesweeper board.
        The move must be known to be safe, and not already a move
        that has been made.

        This function may use the knowledge in self.mines, self.safes
        and self.moves_made, but should not modify any of those values.
        """
        for safe in self.safes:
            if safe not in self.moves_made:
                return safe

        return None

    def make_random_move(self):
        """
        Returns a move to make on the Minesweeper board.
        Should choose randomly among cells that:
            1) have not already been chosen, and
            2) are not known to be mines
        """
        moves = len(self.moves_made) + len(self.mines)
        if moves == 64:
            return None
        while True:
            i = random.randrange(self.height)
            j = random.randrange(self.height)
            if (i, j) not in self.moves_made and (i, j) not in self.mines:
                return (i, j)

runner.py

import pygame
import sys
import time

from minesweeper import Minesweeper, MinesweeperAI

HEIGHT = 8
WIDTH = 8
MINES = 8

# Colors
BLACK = (0, 0, 0)
GRAY = (180, 180, 180)
WHITE = (255, 255, 255)

# Create game
pygame.init()
size = width, height = 600, 400
screen = pygame.display.set_mode(size)

# Fonts
OPEN_SANS = "assets/fonts/OpenSans-Regular.ttf"
smallFont = pygame.font.Font(OPEN_SANS, 20)
mediumFont = pygame.font.Font(OPEN_SANS, 28)
largeFont = pygame.font.Font(OPEN_SANS, 40)

# Compute board size
BOARD_PADDING = 20
board_width = ((2 / 3) * width) - (BOARD_PADDING * 2)
board_height = height - (BOARD_PADDING * 2)
cell_size = int(min(board_width / WIDTH, board_height / HEIGHT))
board_origin = (BOARD_PADDING, BOARD_PADDING)

# Add images
flag = pygame.image.load("assets/images/flag.png")
flag = pygame.transform.scale(flag, (cell_size, cell_size))
mine = pygame.image.load("assets/images/mine.png")
mine = pygame.transform.scale(mine, (cell_size, cell_size))

# Create game and AI agent
game = Minesweeper(height=HEIGHT, width=WIDTH, mines=MINES)
ai = MinesweeperAI(height=HEIGHT, width=WIDTH)

# Keep track of revealed cells, flagged cells, and if a mine was hit
revealed = set()
flags = set()
lost = False

# Show instructions initially
instructions = True

while True:

    # Check if game quit
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

    screen.fill(BLACK)

    # Show game instructions
    if instructions:

        # Title
        title = largeFont.render("Play Minesweeper", True, WHITE)
        titleRect = title.get_rect()
        titleRect.center = ((width / 2), 50)
        screen.blit(title, titleRect)

        # Rules
        rules = [
            "Click a cell to reveal it.",
            "Right-click a cell to mark it as a mine.",
            "Mark all mines successfully to win!"
        ]
        for i, rule in enumerate(rules):
            line = smallFont.render(rule, True, WHITE)
            lineRect = line.get_rect()
            lineRect.center = ((width / 2), 150 + 30 * i)
            screen.blit(line, lineRect)

        # Play game button
        buttonRect = pygame.Rect((width / 4), (3 / 4) * height, width / 2, 50)
        buttonText = mediumFont.render("Play Game", True, BLACK)
        buttonTextRect = buttonText.get_rect()
        buttonTextRect.center = buttonRect.center
        pygame.draw.rect(screen, WHITE, buttonRect)
        screen.blit(buttonText, buttonTextRect)

        # Check if play button clicked
        click, _, _ = pygame.mouse.get_pressed()
        if click == 1:
            mouse = pygame.mouse.get_pos()
            if buttonRect.collidepoint(mouse):
                instructions = False
                time.sleep(0.3)

        pygame.display.flip()
        continue

    # Draw board
    cells = []
    for i in range(HEIGHT):
        row = []
        for j in range(WIDTH):

            # Draw rectangle for cell
            rect = pygame.Rect(
                board_origin[0] + j * cell_size,
                board_origin[1] + i * cell_size,
                cell_size, cell_size
            )
            pygame.draw.rect(screen, GRAY, rect)
            pygame.draw.rect(screen, WHITE, rect, 3)

            # Add a mine, flag, or number if needed
            if game.is_mine((i, j)) and lost:
                screen.blit(mine, rect)
            elif (i, j) in flags:
                screen.blit(flag, rect)
            elif (i, j) in revealed:
                neighbors = smallFont.render(
                    str(game.nearby_mines((i, j))),
                    True, BLACK
                )
                neighborsTextRect = neighbors.get_rect()
                neighborsTextRect.center = rect.center
                screen.blit(neighbors, neighborsTextRect)

            row.append(rect)
        cells.append(row)

    # AI Move button
    aiButton = pygame.Rect(
        (2 / 3) * width + BOARD_PADDING, (1 / 3) * height - 50,
        (width / 3) - BOARD_PADDING * 2, 50
    )
    buttonText = mediumFont.render("AI Move", True, BLACK)
    buttonRect = buttonText.get_rect()
    buttonRect.center = aiButton.center
    pygame.draw.rect(screen, WHITE, aiButton)
    screen.blit(buttonText, buttonRect)

    # Reset button
    resetButton = pygame.Rect(
        (2 / 3) * width + BOARD_PADDING, (1 / 3) * height + 20,
        (width / 3) - BOARD_PADDING * 2, 50
    )
    buttonText = mediumFont.render("Reset", True, BLACK)
    buttonRect = buttonText.get_rect()
    buttonRect.center = resetButton.center
    pygame.draw.rect(screen, WHITE, resetButton)
    screen.blit(buttonText, buttonRect)

    # Display text
    text = "Lost" if lost else "Won" if game.mines == flags else ""
    text = mediumFont.render(text, True, WHITE)
    textRect = text.get_rect()
    textRect.center = ((5 / 6) * width, (2 / 3) * height)
    screen.blit(text, textRect)

    move = None

    left, _, right = pygame.mouse.get_pressed()

    # Check for a right-click to toggle flagging
    if right == 1 and not lost:
        mouse = pygame.mouse.get_pos()
        for i in range(HEIGHT):
            for j in range(WIDTH):
                if cells[i][j].collidepoint(mouse) and (i, j) not in revealed:
                    if (i, j) in flags:
                        flags.remove((i, j))
                    else:
                        flags.add((i, j))
                    time.sleep(0.2)

    elif left == 1:
        mouse = pygame.mouse.get_pos()

        # If AI button clicked, make an AI move
        if aiButton.collidepoint(mouse) and not lost:
            move = ai.make_safe_move()
            if move is None:
                move = ai.make_random_move()
                if move is None:
                    flags = ai.mines.copy()
                    print("No moves left to make.")
                else:
                    print("No known safe moves, AI making random move.")
            else:
                print("AI making safe move.")
            time.sleep(0.2)

        # Reset game state
        elif resetButton.collidepoint(mouse):
            game = Minesweeper(height=HEIGHT, width=WIDTH, mines=MINES)
            ai = MinesweeperAI(height=HEIGHT, width=WIDTH)
            revealed = set()
            flags = set()
            lost = False
            continue

        # User-made move
        elif not lost:
            for i in range(HEIGHT):
                for j in range(WIDTH):
                    if (cells[i][j].collidepoint(mouse)
                            and (i, j) not in flags
                            and (i, j) not in revealed):
                        move = (i, j)

    # Make move and update AI knowledge
    if move:
        if game.is_mine(move):
            lost = True
        else:
            nearby = game.nearby_mines(move)
            revealed.add(move)
            ai.add_knowledge(move, nearby)

    pygame.display.flip()

我知道这就是错误发生的地方，用副本替换迭代对象可以解决问题。问题是我看不到我在哪里编辑的设置在第一位

class MinesweeperAI:
    def updateknowledge(self):
        ...
        safes = sentence.known_safes()
        if safes:
            keepgoing = True
            for safe in safes.copy():
                self.mark_safe(safe)

self.mark_safe(safe)导致（扫雷艇类）

self.safes.add(cell)
        for sentence in self.knowledge:
            sentence.mark_safe(cell)

和sentence.mark_safe(cell)导致

if cell in self.cells:
            self.cells.remove(cell)

那么这是如何影响我正在迭代的safes集的呢？非常感谢您的建议

Answer 1

问题是，代码在“保险柜”上循环时“标记保险柜”

尝试更改：

for safe in self.safes:

致：

for safe in list(self.safes):

这将使“保险箱”的副本循环，使基础集可用于更新