在python中检查二维列表中的变量

Question

I'm trying to get the user to input a number from 1 to 9. The code is supposed to check if the number is in the list "board" or already taken. If it's not taken the number is turned into "O". If the number is not in the list or already taken the loop is supposed to re-ask the user for input. However, even if the number is in the list and not taken, the function asks the user for input twice. If I move the else statement on line with the if statement, I get an infinite loop asking for input.

Here's the code:

# ask the unser to make a move
def userMove():
    move = int(input("Please make your move: "))
    check = True
    # check if move is already taken
    while check:
        for i in range(len(board)):
                for j in range(len(board[i])):
                    if board[i][j] == move:
                        board[i][j] = "O"
                        check = False
        else:
            print("This field is either already taken or not on the board")
            move = int(input("Please choose another move: "))

Answer 1

您可以使用any()检查值是否在二维列表中：

if any(move in sublist for sublist in board):

Answer 2

Your problem is caused by the else clause being executed always. The posted code can be fixed as follows.

• With for/else statements, the else clause executes after the loop completes normally.
• A break statement can be used to prevent normal completion.

Revised Code

# ask the unser to make a move
def userMove():
    move = int(input("Please make your move: "))
    check = True
    # check if move is already taken
    while check:
        for i in range(len(board)):
                for j in range(len(board[i])):
                    if board[i][j] == move:
                        board[i][j] = "O"
                        check = False
                        break
                if not check:
                    break
        else:
            # only executes if break not encountered in for i loop
            print("This field is either already taken or not on the board")
            move = int(input("Please choose another move: "))