0

this is a past yr mid-term exam qns, around the topic of data abstraction. I'm limited to only using tuples and these are the functions I was guided to define.

make_state() creates empty state object for game

get_square(s,x,y) will return symbol in the game state object s at the grid location(x,y) where 0<_x,y<_2. If grid empty, function returns None

move(s,x,y,player) returns a new state object after player(where player either 'X' or 'O' makes a move at the grid location (x,y). If the move is invalid, False is returned instead.

check_rep(s) return True if s is a valid game state object, or False otherwise.

def make_state():
    return ((0,0,0),(0,0,0),(0,0,0))

def get_square(s,x,y):
    if s[x][y]==0:
        return None
    elif s[x][y]==1:
        return 'X'
    elif s[x][y]==2:
        return 'O'

def check_rep(s):
    if len(s)!=3:
        return False
    for row in s:
        if len(row)!=3:
            return False
        for col in row:
            if col not in (0,1,2):
                return False
    return True

The problem comes when I have to implement move(s,x,y,player)

def move(s,x,y,player):
if check_rep(s)==False:
    return False
elif get_square(s,x,y):
    return False
elif player not in ('X','O'):
    return False
symbol=1
if player=='O':
    symbol=2
a,b=0,0
for row in s:
    for col in row:   
        if x==a and y==b:
            new_row=row[:y]+(symbol,)+row[y+1:]
            return s[:x]+(new_row,)+s[x+1:]
        b+=1

    a+=1

My test cases

s=make_state()
s1=move(s,0,0,'X')
s2=move(s1,1,1,'X')
s3=move(s2,2,2,'O')

Error messages from Python seem to show s2 is a NoneType object, can someone tell me why it will end up as None?

Prashin Jeevaganth
  • 1,223
  • 1
  • 18
  • 42
  • Why don't you debug it yourself? Why do you expect that we will be able to debug it better than you? – user202729 Mar 08 '18 at 02:28
  • [Python debugging tips](https://stackoverflow.com/questions/1623039/python-debugging-tips). Well, the debugger can tell you that. – user202729 Mar 08 '18 at 02:30
  • [Meta: Can we support users who do not understand how to debug their code?](https://meta.stackoverflow.com/questions/364282/can-we-support-users-who-do-not-understand-how-to-debug-their-code) (this one is better, as the code necessary for reproducing the problem are fully included in the question) – user202729 Mar 08 '18 at 02:31

1 Answers1

0

First, is it supposed to be printing numbers on the board or X's and O's?

Anyways, you're increasing the b value each time and not resetting as you go through a new row. Try this:

for row in s:
    b = 0
    for col in row:

This should fix your problem. It is going through the function, but it's never hitting a return statement

Connor John
  • 433
  • 2
  • 8
  • The qns only wants get_square to work so I dont think using 0,1,2 matters as long as get_square shows the right thing, Anyway thanks for your help, that seems to be the only problem, missing out the fact that value of b has to be rinsed whenever I iterate through a new row. – Prashin Jeevaganth Mar 08 '18 at 03:17