Gomoku game (also called Five in a Row)

Gomoku.py

class Gomoku:
	def __init__(self, size):
		self.size = size
		self.board = ['-'] * size * size
		self.inarow = 5
		self.players = ['x', 'o']
		self.curplayer = 1

	def printboard(self):
		s = self.size
		b = self.board

		print(' '.join(map(str, range(s+1)))) # print column numbers

		for i in range(s):
			# row number plus the row itself
			# add spaces to make the board look square
			print(str(i+1) + ' ' + ' '.join(b[i*s : (i+1)*s]))

	def aimove(self): # IMPROVE!
		import random
		placed = False

		# rudimentary AI, try and place an 'o' closer to most of the 'x's
		count = 1
		avgix = self.size/2 + 1 # initial estimate for row where 'x's congregate
		avgjx = self.size/2 + 1 # initial estimate for column where 'x's congregate
		for i in range(self.size):
			for j in range(self.size):
				index = i*self.size + j
				if self.board[index] == 'x':
					avgix = (avgix*count + i) / (count + 1)
					avgjx = (avgjx*count + j) / (count + 1)
					count += 1

		sigma = 0.1 # normal distribution, sigma adjusted as space gets crowded
		while not placed:
			i, j = -1, -1
			while not 0<=i<self.size:
				i = int(random.gauss(avgix, sigma) + 1) 
			while not 0<=j<self.size:
				j = int(random.gauss(avgjx, sigma) + 1)

			index = i*self.size + j
			if self.board[index] == '-':
				placed = True
			sigma += 0.1

		return (i, j)

	def win(self):
		k = self.inarow
		n = self.size
		if n < k:
			print("The board is too small, we can't play.")
			return True

		'''
		rows
		0,0 -> k ... 0,n-k
		...
		n-1,0 ... n-1,n-k
		'''
		for i in range(n):
			for j in range(n-k+1):
				index = i*n + j
				match = True
				for m in range(k-1):
					# starting from index, check 5 to the right
					cur = index + m
					nxt = index + m+1
					if (self.board[cur] != self.board[nxt]
							or self.board[cur] == '-'):
						match = False
						break
				if match:
					return True

		'''
		columns
		0,0 ... 0,n-1
		 | 
		 k 
		 ...
		n-k,0 ... n-k,n-1
		'''
		for i in range(n-k+1):
			for j in range(n):
				index = i*n + j
				match = True
				for m in range(k-1):
					# starting from index, check 5 down
					cur = index + m*n
					nxt = index + (m+1)*n
					if (self.board[cur] != self.board[nxt]
							or self.board[cur] == '-'):
						match = False
						break
				if match:
					return True

		'''
		forward diagonals
		0,0 ... 0,n-k
			\
		...  k
		n-k,0 ... n-k,n-k
		'''
		for i in range(n-k+1):
			for j in range(n-k+1):
				index = i*n + j
				match = True
				for m in range(k-1):
					# starting from index, check 5 down and to the right
					cur = index + m*(n+1)
					nxt = index + (m+1)*(n+1)
					if (self.board[cur] != self.board[nxt]
							or self.board[cur] == '-'):
						match = False
						break
				if match:
					return True

		'''
		backwards diagonals
			 k
			/
		n-k,0 ... n-k,n-k
		...
		n-1,0 ... n-1,n-k
		'''
		for i in range(n-k, n):
			for j in range(n-k+1):
				index = i*n + j
				match = True
				for m in range(k-1):
					# starting from index, check 5 up and to the right
					cur = index + m*(-n+1)
					nxt = index + (m+1)*(-n+1)
					if (self.board[cur] != self.board[nxt]
							or self.board[cur] == '-'):
						match = False
						break
				if match:
					return True
		return False

	def getnext(self):
		i, j = 0, 0

		if self.curplayer == 0: # AI's move
			self.curplayer = 1
			player = self.players[self.curplayer]
			i, j = self.aimove()
			cell = i*self.size + j
			self.board[cell] = player
			gomoku.printboard()

		else: # human's move
			self.curplayer = 0
			player = self.players[self.curplayer]

			placed = False
			while not placed:
				try:
					j = int(raw_input("Column # for " + player + ", please: "))
					i = int(raw_input("Row # for " + player + ", please: "))
				except ValueError:
					print("Must be a number. Try again?")
					continue

				if 0 <= i < self.size and 0 <= j < self.size:			
					index = i*self.size + j

					if self.board[index] == '-':
						self.board[index] = player
						placed = True
						gomoku.printboard()
					else:
						print("That wasn't a valid move. Try again? ") 
				else:
					print("Must be a number between 1 and " + \
						str(self.size + 1) + ". Try again? ") 


if __name__ == '__main__':
	assert Gomoku(1) != None
	assert Gomoku(1).size == 1
	assert Gomoku(1).win() == True
	assert Gomoku(4).win() == True
	g = Gomoku(5)
	assert g.win() == False
	print("All tests passed, let's play.")

	gomoku = Gomoku(9)
	gomoku.printboard()

	while not gomoku.win():
		gomoku.getnext()

	gomoku.printboard()
	print("Player " + gomoku.players[gomoku.curplayer] + " won the game!")