如何在完全不同的函数中使用函数的返回值

Question

I am writing a tic-tac-toe game and currently have the following functions:

 # Need: Board, Display Board, Play Game, Alternating Terms, Os, Xs, Wins, Losses

board = ["-", "-", "-",
         "-", "-", "-",
         "-", "-", "-", ]


def display_board():
    print(board[0] + " | " + board[1] + " | " + board[2])
    print(board[3] + " | " + board[4] + " | " + board[5])
    print(board[6] + " | " + board[7] + " | " + board[8])


def handle_turn():
    position = input("\nChoose a position from 1 to 9: ")
    position = int(position) - 1
    return position


def choose_player_marker(marker):
    player_marker = ''
    if marker == 'X' or marker == 'x':
        player_marker = 'X'
        return player_marker
    elif marker == 'O' or marker == 'o':
        player_marker = 'O'
        return player_marker


def opp_move():
    opp_marker = ''
    if choose_player_marker() == 'X':
        opp_marker = 'O'
    else:
        opp_marker = 'X'


def play_game():
    game_current = True
    display_board()
    marker = input("\nPlease choose a marker: 'X' or 'x' OR 'O' or 'o' : ")
    choose_player_marker(marker)
    opp_move()
    handle_turn()


play_game()

In the function def choose_player_marker(marker): I return player_marker = 'X' or player_marker = 'O' , depending on the condition.

I would like to use the resulting 'X' or 'O' in the function def opp_move(): to determine which marker the opponent will choose. However, I am having difficulty in properly delegating the return statement. I tried using marker as the argument in the def opp_move(): function and also have tried if choose_player_marker(marker) == 'X' to no avail.

How do I correctly handle the return statement from def choose_player_marker(marker): so that my def opp_move(): function will be able to determine what marker the opponent will choose?

Answer 1

Now we can see your full code, the solution is simple.

You already call choose_player_marker() in main . You don't need to call it in opp_move as well. What you need to do instead is to capture the result when you call it in main, and then pass in the value to opp_move:

def opp_move(marker):
    if marker == 'X':
        opp_marker = 'O'
    else:
        opp_marker = 'X'
    return opp_marker


def play_game():
    game_current = True
    display_board()
    marker = input("\nPlease choose a marker: 'X' or 'x' OR 'O' or 'o' : ")
    marker = choose_player_marker(marker)
    opp_move(marker)
    handle_turn()

Now there are various other things wrong with this code, like the fact that handle_turn doesn't do anything useful, and that as others have pointed out choose_player_marker can be trivially replaced with a call to marker.upper() , but at least this should get you going.

Answer 2

The function choose_player_marker doesn't do anything useful at present. If you give it an X it gives you back and X , if you give it an O it gives you back an O . The only use it has right now is converting lowercase x and o to uppercase X and O.

Thus there is no need to call it, because if we know the input (X) then we know the output (X).

Given the name: choose_player_marker I suspect you want either a different name (eg normalise_player_marker() or a different implementation, ie one that prompts for user-input asking the person if they want to be X or O?)

As for opp_move : There's no need to call choose_player_marker . If you know the player is X then you know the opponent is O , and vice versa. Thus I suspect you want something like this:

def normalise_marker(marker):
    if marker == 'X' or marker == 'x':
        return 'X'
    elif marker == 'O' or marker == 'o':
        return 'O'

def opp_move(player_marker):
    opp_marker = ''
    normed_marker = normalise_marker(player_marker)
    if normed_marker == 'X':
        opp_marker = 'O'
    else:
        opp_marker = 'X'
    # use opp_marker here

Note that in its current state normalise_marker doesn't handle the case of marker NOT being an X or O, and can be reduced to an even simpler implementation, but that is left as an exercise for you :)

Answer 3

Im not familiar with Python, but I guess it would make it more simple if the provided argument was set to lower case, the additional check for Capital case wouldn't be needed. Still You could probably shorten the code this way.

def choose_player_marker(marker):
    return marker.lower()

def opp_move(result):
if result == 'x':
    return 'o'
else:
    return 'x'

playerMarker = 'X'
res = choose_player_marker(playerMarker)
opp = opp_move(res)
print(result, opp)