second if statement returns result, first if statement doesn't

Question

In the code below, the when check_result returns true, I want my program to terminate. However, when check_result(p1) returns True the print statement prints, but the program carries on.

BUT if check_result(p2) returns True, the statement gets printed and program terminates. Please help me figure out why the first one doesn't work Thanks!

while game_on:

        p1_turn = int(input(f"Player 1, choose a number between 1 and 9\n"))
        matrix[p1_turn - 1] = "X"
        p1.append(p1_turn)
        place_mark(matrix)
        if check_result(p1):
            print("Player 1 wins")
            game_on = False

        p2_turn = int(input(f"Player 2, choose a number between 1 and 9\n"))
        matrix[p2_turn - 1] = "0"
        p2.append(p2_turn)
        place_mark(matrix)
        if check_result(p2):
            print("Player 2 wins")
            game_on = False

Answer 1

just put a break statement. and the game_on variable is uneccessary. just use while 1 that is slightly faster than while True.

while 1:
    p1_turn = int(input(f"Player 1, choose a number between 1 and 9\n"))
    matrix[p1_turn - 1] = "X"
    p1.append(p1_turn)
    place_mark(matrix)
    if check_result(p1):
        print("Player 1 wins")
        break

    p2_turn = int(input(f"Player 2, choose a number between 1 and 9\n"))
    matrix[p2_turn - 1] = "0"
    p2.append(p2_turn)
    place_mark(matrix)
    if check_result(p2):
        print("Player 2 wins")
        break

Answer 2

if check_result(p1):
    print("Player 1 wins")
    game_on = False

Do you see any break statement here? The while loop won't break by itself.

if check_result(p1):
    print("Player 1 wins")
    game_on = False
    break

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You can anyway completely replace this game_on variable with a break statement:

if check_result(p1):
    print("Player 1 wins")
    break

if check_result(p2):
    print("Player 2 wins")
    break

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If you want to know better the usage of break (and maybe of continue) read this.