python：如何替换嵌套字符串列表中的字符串

Question

我正在尝试替换嵌套列表中的字符串。

board = [
['O', 'X', '.'],
['.', 'O', 'X'],
['.', 'O', 'X']
]

这最终会像

一样

board = [
['O', '*', '.'],
['.', 'O', '*'],
['.', 'O', '*']
]

这是我尝试过的：

    new_board = [[x.replace('X', '*') for x in l] for l in board]

它就像这样作为一个单一的assingment，但当我尝试在一个函数中做它不起作用。该功能必须修改给定的电路板;它返回None。

def change_player_char(board, player, new_char):

    board = [[new_char if j == player else j for j in i] for i in board]

我称之为：

board = [
['O', 'X', '.'],
['.', 'O', 'X'],
['.', 'O', 'X']
]

change_player_char(board, 'X', '*')
for row in board:
    print(row)

Answer 1

[['*' if j=='X' else j for j in i] for i in board]
#[['O', '*', '.'], ['.', 'O', '*'], ['.', 'O', '*']]

Answer 2

您可以使用map：

board = [
 ['O', 'X', '.'],
 ['.', 'O', 'X'],
 ['.', 'O', 'X']
]
new_board = [list(map(lambda x:"*" if x == "X" else x, i)) for i in board]

输出：

[['O', '*', '.'], 
 ['.', 'O', '*'], 
 ['.', 'O', '*']]