I am new to python and I am trying to build a simple Tic-Tac-Tock game.When I am taking input from user it goes to infinity loop

Question

def player_input():
    player1=''
    player2=''
    while player1 != "X" or player1 !="O":
        player1=input('Choose from X or O').upper()

    if player1=='X':
        player2 = 'O'
        return (player1,player2)
    elif player1=='O':
        player2='X'
        return (player1,player2)

When I am running it is going to infinity loop. But,when I am changing my while loop to while not(player1 =="X" or player1=="O") my code is running fine. So can someone explain the difference between my both while loop?

You might want to use a [debugger](https://stackoverflow.com/questions/25385173/what-is-a-debugger-and-how-can-it-help-me-diagnose-problems) for that or look at [How to debug small programs](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/) — Andreas, Sep 20 '19 at 03:55
`player1 != "X" or player1 !="O"`: This is a tautology (i.e. it is always `True`). Think about it. — Selcuk, Sep 20 '19 at 04:04

lmiguelvargasf · Accepted Answer · 2019-09-20T04:14:09.220

Your condition is wrong, you basically want to be in the while loop until the user enters either X or O. Thus, this means:

not (player1 == "X" or player1 =="O")

This might be a bit confusing specially if you are not familiar with boolean algebra. Basically you have the following:

X and Y, so not (X and Y) is logically equivalent to not X or not Y. In your case you have:

not (player1 == "X" or player1 =="O")

which is logically equivalent to:

player1 != "X" and player1 != "O"

If you want to know more about this, you can read about De Morgan's laws

I am new to python and I am trying to build a simple Tic-Tac-Tock game.When I am taking input from user it goes to infinity loop

1 Answers1