Python中如何实现数组更新：创建新数组且原数组保持不变

问题背景 #

开发填字游戏相关功能时，定义了用于表示棋盘方格的Square类：类实例具备x/y坐标、方格字符、标记序号属性，可通过实例的write方法修改方格上的字符内容。开发数组更新逻辑时出现异常行为：尝试基于原方格数组创建新数组、通过write方法在新数组上写入单词时，原数组与新数组的方格内容会发生同步变更。

多轮定位排查过程 #

• 最初版本直接将原数组赋值给临时变量执行写入操作，未做独立拷贝
• 尝试为write_word函数添加数组浅拷贝操作后测试，同步修改的问题仍然存在
• 后续改用嵌套列表替代numpy数组存储方格对象，分别实现了基于numpy数组和Python列表版本的棋盘创建、单词写入逻辑，两种实现下问题表现完全一致：创建原始棋盘、对棋盘做拷贝后修改拷贝对象的内容，原始棋盘的内容会同步变化。由此判断问题根源并非数组或列表数据结构本身，而是自定义类对象的引用传递特性
• 测试发现numpy数组与Python列表在浅拷贝场景下会出现相同的同步修改问题，最终在不修改Square类逻辑的前提下实现了符合预期的功能

相关实现代码 #

核心方格类定义 #

class Square:
    def __init__(self, x,y):
        self.x = x
        self.y = y
        self.letter = " "
        self.num = 0
        
    def write(self, letter):
        if self.letter != "!":
            self.letter = letter.upper()
        else:
            print("cannot write on black square")
    def clear(self):
        if self.letter != "!":
            self.letter = " "
        else:
            print("cannot write on black square")
    def black(self):
        self.letter = "!"
    def isblack(self):
        if self.letter == "!":
            return True
        else:
            return False
    def isfilled(self):
        if self.letter != "!" and self.letter != " ":
            return True
        else:
            return False
    def read(self):
        return self.letter
    def number(self,num):
        self.num = num
    def getnum(self):
        return self.num
    def __str__(self):
        image = "  " + self.letter
        return image
    def __repr__(self):
        image = "  " + self.letter
        return image

存在问题的版本实现 #

1. 无独立拷贝的numpy数组写入逻辑

def write_word(crossarray,indexes,word):
    print("now writing word:",word)
    temparray = crossarray
    for i, index in enumerate(indexes):
        row = int(index // 5)
        col = int(index % 5)
        temparray[row,col].write(word[i])
    return temparray

2. 浅拷贝的numpy数组写入逻辑

def UPDATED_write_word(crossarray,indexes,word):
    print("now writing word:",word)
    temparray = crossarray.copy()
    for i, index in enumerate(indexes):
        row = int(index // 5)
        col = int(index % 5)
        temparray[row,col].write(word[i])
    return temparray

3. numpy数组版本的棋盘创建逻辑

def create_crossword(down,across,indexes,blacks):
    cross_array =  np.zeros((5,5), dtype=Square)
    for row in range(len(cross_array)):
        for col in range(len(cross_array[0])):
            cross_array[row,col] = Square(row,col)
    
    for name, index in enumerate(indexes):
        row = int(index // 5)
        col = int(index % 5)
        cross_array[row,col].number(name+1)
    
    for index in blacks:
        row = int(index // 5)
        col = int(index % 5)
        cross_array[row,col].black()
    return(cross_array)

4. Python列表版本的棋盘创建与写入逻辑

def create_crosslist(down,across,indexes,blacks):
    cross_list = []
    for row in range(5):
        rowlist = []
        for col in range(5):
            rowlist.append(Square(row,col))
        cross_list.append(rowlist)
    
    for name, index in enumerate(indexes):
        row = int(index // 5)
        col = int(index % 5)
        cross_list[row][col].number(name+1)
    
    for index in blacks:
        row = int(index // 5)
        col = int(index % 5)
        cross_list[row][col].black()
    return cross_list

def write_word_list(crosslist,indexes,word):
    print("now writing word:",word)
    templist = crosslist
    for i, index in enumerate(indexes):
        row = int(index // 5)
        col = int(index % 5)
        templist[row][col].write(word[i])
    return templist

最终生效的实现 #

通过copy.deepcopy做深度拷贝，完全断开原对象与拷贝对象的引用关联，无需修改Square类逻辑即可实现棋盘独立修改的效果：

import copy
def FINAL_write_word(crossarray,indexes,word):
    print("now writing word:",word)
    temparray = copy.deepcopy(crossarray)
    for i, index in enumerate(indexes):
        row = int(index // 5)
        col = int(index % 5)
        temparray[row,col].write(word[i])
    return temparray

内容的提问来源于stack exchange，提问作者Lara Ipek