Python for循环过滤失效：遇到字典fence指定值时未终止添加操作

你代码的核心错误出在边界判断的逻辑写法：

if number in (
    fence["top_fence"]
    or fence["bottom_fence"]
    or fence["right_fence"]
    or fence["left_fence"]
):

Python中or是布尔逻辑运算符，括号内的表达式会先执行运算：只要fence["top_fence"]非空（此处显然非空），整个括号的返回结果就只有fence["top_fence"]，剩下三个边界列表完全不会被纳入判断。也就是说你实际上只校验了当前值是否在顶部边界，碰到左、右、底部边界时判断都不会触发，break自然不会执行。

方案1：直接修正判断逻辑 #

把判断条件改为分别校验每个边界列表：

if number in fence["top_fence"] or number in fence["bottom_fence"] or number in fence["right_fence"] or number in fence["left_fence"]:

也可以用any()函数简化写法：

if any(number in fence_line for fence_line in fence.values()):

方案2：优化查询效率（推荐） #

提前把所有边界值合并为一个集合，集合的in查询时间复杂度为O(1)，比多次遍历列表效率更高：

# 提前合并所有边界值为集合
all_fence = set(num for line in fence.values() for num in line)

# 循环内判断改为
if number in all_fence:

你当前的代码逻辑是先把位置追加到合法列表，再判断是否为边界，因此边界值本身也会被存入possible_moves_within_fence。如果需求是边界不属于合法移动位置，需要把追加操作放到判断之后：

for number in possible_moves["tower"][key]:
    if number in all_fence:
        print(number)
        break
    possible_moves_within_fence[key].append(number)

fence = {
    "right_fence": list(range(8, 65, 8)),
    "left_fence": list(range(1, 58, 8)),
    "top_fence": list(range(1, 9)),
    "bottom_fence": list(range(56, 65)),
}
# 提前合并边界集合
all_fence = set(num for line in fence.values() for num in line)

# 棋子可移动的可能位置
possible_moves = {
    "tower": {
        "left-down": list(range(self.place_of_brick, 65, 7)),
        "left-up": list(range(self.place_of_brick, 1, -9)),
        "right-down": list(range(self.place_of_brick, 65, 9)),
        "right-up": list(range(self.place_of_brick, 1, -7)),
    }
}

possible_moves_within_fence = {
    "left-down": list(),
    "left-up": list(),
    "right-down": list(),
    "right-up": list(),
}

for key in possible_moves["tower"].keys():
    for number in possible_moves["tower"][key]:
        # 若不需要把边界加入合法列表，调整下面两行的顺序即可
        possible_moves_within_fence[key].append(number)
        if number in all_fence:
            print(number)
            break

内容的提问来源于stack exchange，提问作者Dolphin