'''
Auf diese Art kann die Klasse verwendet werden:

>>> ttt = TicTacToe()
>>> ttt.stones
{}
>>> ttt.place_x_at(1,1)
>>> ttt.place_o_at(0,0)
>>> ttt.stones
{(1, 1): 'x', (0, 0): 'o'}
>>> ttt.x_wins()
False
>>> ttt.o_wins()
False
>>> ttt.place_x_at(0,1)
>>> ttt.place_o_at(1,0)
>>> ttt.place_x_at(2,1)
>>> ttt.x_wins()
True
>>> ttt.o_wins()
False
>>> ttt.stones
{(1, 1): 'x', (0, 0): 'o', (0, 1): 'x', (1, 0): 'o', (2, 1): 'x'}
'''

import doctest

class TicTacToe:
    'A game of tic tac toe.'

    def __init__(self):
        # mapping (x,y) to 'x' or 'o'
        self.stones = {}

    def place_x_at(self, x, y):
        assert 0 <= x <= 2 and 0 <= y <= 2
        self.stones[(x, y)] = "x"

    def place_o_at(self, x, y):
        assert 0 <= x <= 2 and 0 <= y <= 2
        self.stones[(x, y)] = "o"

    def x_wins(self):
        'Return whether player x has three in a row.'

    def o_wins(self):
        'Return whether player o has three in a row.'




ttt = TicTacToe()
'''
o.x
xxo
x.o
'''
for x, y in [(2, 0), (1, 0), (1, 1), (0, 2)]:
    ttt.place_x_at(x, y)
for x, y in [(0, 0), (2, 1), (2, 2)]:
    ttt.place_o_at(x, y)
assert len(ttt.stones) == 7
assert ttt.x_wins()
assert not ttt.o_wins()

doctest.testmod()  # running tests from class documentation