Issues with storing variables outside of a function

[cerulean747]

Hi all,

Python newbie here. I'm confused as to why after running the below function, when I call one of the variables defined within that function, I receive an error message (that the variable is undefined). My code is below:

    def player_input():
    player1_mark = input("Please pick a marker 'X' or 'O'")
    player2_mark = ''
    if player1_mark=='X':
        player2_mark='O'
    elif player1_mark=='O':
        player2_mark='X'
    print("Player 1 is: " + player1_mark)
    print("Player 2 is: " + player2_mark)

In particular, after defining player1_mark, I get an undefined error when I try to retrieve "player2_mark" outside of the function, even though executing the function successfully prints both variables. Can anyone help out with this? Thanks!