[英]Strange behavior with lists in Python
I have noticed that probability_matrix
seems to become adapted_given_board
despite never being assigned it.我注意到
probability_matrix
似乎变成adapted_given_board
,尽管它从未被分配过。
def build_probability_matrix(self):
r = 0
p = -1
adapted_given_board = self.probability_matrix
print(self.game.board.given_board)
for i in range(len(self.game.board.given_board)-1):
p += 1
if self.game.board.given_board[i] == '\n':
r += 1
p = -1
else:
adapted_given_board[r][p] = self.game.board.given_board[i]
print(adapted_given_board)
This assignment:本次作业:
adapted_given_board = self.probability_matrix
is a reference, not a copy.是参考,不是副本。 That is, you're creating a new name for
self.probability_matrix
, not a new list that has a copy of the contents.也就是说,您正在为
self.probability_matrix
创建一个新名称,而不是一个包含内容副本的新列表。
So when you do:所以当你这样做时:
adapted_given_board[r][p] = self.game.board.given_board[i]
it's the exact same as if you'd done:这与您所做的完全相同:
self.probability_matrix[r][p] = self.game.board.given_board[i]
Be careful about trying to use copy
to fix this, since you're working with two-dimensional lists;尝试使用
copy
来解决此问题时要小心,因为您正在使用二维列表; you might end up just pushing the problem down one level.你最终可能只是把问题推低了一层。 There is such a thing as
deepcopy
, but here's one idea for a very minimal fix that just allocates new entries in the matrix before you assign to them:有这样的东西
deepcopy
,但这里有一个非常小的修复的想法,它只是在分配给矩阵之前分配矩阵中的新条目:
def build_probability_matrix(self):
r = 0
p = -1
adapted_given_board = [[]] # start with one row that has zero cells
print(self.game.board.given_board)
for i in range(len(self.game.board.given_board)-1):
p += 1
adapted_given_board[r].append(None) # add a cell
if self.game.board.given_board[i] == '\n':
r += 1
adapted_given_board.append([]) # add a row
p = -1
else:
adapted_given_board[r][p] = self.game.board.given_board[i]
print(adapted_given_board)
Or you could simply append your new elements rather than assigning them by index...或者您可以简单地 append 您的新元素,而不是按索引分配它们......
def build_probability_matrix(self):
adapted_given_board = [[]]
print(self.game.board.given_board)
for element in self.game.board.given_board:
if element == '\n':
adapted_given_board.append([])
else:
adapted_given_board[-1].append(element)
print(adapted_given_board)
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