オセロのエラーが取れない python3

python3
1from pprint import pprint
2import random
3board = [[0 for _ in range(8)]for _ in range(8)]
4
5board[3][3] = 1
6board[4][4] = 1
7board[3][4] = -1
8board[4][3] = -1
9
10#黒=1 , 白=-1, 無し=0
11
12def can_put(black_or_white,board):
13	if black_or_white == 1:
14		put = 1
15	else:
16		put = -1
17
18	#
19	x = [-1,0,1,0,-1,1,-1,1]
20	y = [0,1,0,-1,1,1,-1,-1]
21	return_list =[]
22	for i in range(8):
23		for j in range(8):
24			for k in range(4):
25				times = 1
26				temp_list = [[i,j]]
27				for _ in range(7):
28					X = i+x[k]*times
29					Y = i+y[k]*times
30					if 0>X or X>7:
31						break
32					if 0>Y or Y>7:
33						break
34					if times >1:
35						if board[X][Y] == put:
36							return_list = temp_list
37							break
38					#print(X,Y)
39					if board[X][Y] == put*(-1):
40						temp_list.append([X,Y])
41						times += 1
42					if len(return_list) > 1:
43						return True
44	return False
45
46
47
48def return_output(black_or_white,i,j,board):
49	#
50	if black_or_white == 1:
51		put = 1
52	else:
53		put = -1
54
55	x = [-1,0,1,0,-1,1,-1,1]
56	y = [0,1,0,-1,1,1,-1,-1]
57	return_list = []
58	for k in range(len(x)):
59		times = 1
60		temp_list = [[i,j]]
61
62		for _ in range(7):
63			X = i+x[k]*times
64			Y = i+y[k]*times
65			print(X,Y)
66			if 0>X or X>8:
67				break
68			if 0>Y or Y>8:
69				break
70			if times >1:
71				if board[X][Y] == put:
72					return_list = temp_list
73					return return_list
74							
75			if board[X][Y] == put*(-1):
76				temp_list.append([X,Y])
77				times += 1
78
79
80
81def update(black_or_white,return_list,board):
82	print(return_list)
83	for i in range(len(return_list)):
84		x = return_list[i][0]
85		y = return_list[i][1]
86		board[x][y] = black_or_white
87	return board
88
89def black_strategy(board):
90	
91	return 2,4
92
93def white_strategy(board):
94	return 2,3
95
96def judge(board):
97	b = 0
98	w = 0
99	for i in range(8):
100		for j in range(8):
101			if board[i][j] == 1:
102				b += 1
103			elif board[i][j] == -1:
104				w += 1
105	return b,w
106
107def main(board):
108	black = 1
109	white = -1
110	while True:
111	#can_put(black,board) or can_put(white,board):
112		while True:
113		#can_put(black):
114			output = black_strategy(board)
115			board = update(
116					black,
117					return_output(black,output[0],output[1],board),
118					board
119					)
120
121		while True:
122		#can_put(white):
123			output = white_strategy(board)
124			board = update(
125					white,
126					return_output(white,output[0],output[1],board),#リスト
127					board
128					)
129
130	black_score,white_score = judge(board)
131
132	if black_score > white_score:
133		print("win:black"+str(black_score)+"-"+str(white_score))
134	elif black_score < white_score:
135		print("win:white"+str(black_score)+"-"+str(white_score))
136	else:
137		print("even:"+str(black_score)+"-"+str(white_score))
138	pprint(board)
139
140main(board)
141> None
142Traceback (most recent call last):
143  File "othello1.py", line 140, in <module>
144    main(board)
145  File "othello1.py", line 118, in main
146    board
147  File "othello1.py", line 83, in update
148    for i in range(len(return_list)):
149TypeError: object of type 'NoneType' has no len()