Python 3 子元素列表比较

Question

我有一个包含以下元素的列表

queue = [[(1, 5), 4, (1, 4)], [(2, 2), 6, (2, 3)], 
         [(1, 3), 6, (2, 3)], [(1, 3), 6, (1, 4)]]

还有一个叫

neighbors = [[(1, 5), 4, (1, 4)], [(1, 3), 6, (1, 4)], 
             [(2, 4), 4, (1, 4)], [(0, 4), 6, (1, 4)]]

如何检查第二个列表中的第一个元组元素是否存在于第一个中？

通常我会这样做：

for item in neighbors:
    if item[0] in queue:
        Do something...

但这缺少了一些东西。

Answer 1

在queue 中建立索引，例如：

queue_exists = set(q[0] for q in queue)

然后测试queue中是否有类似：

if item[0] in queue_exists:

测试代码：

queue = [[(1, 5), 4, (1, 4)], [(2, 2), 6, (2, 3)], [(1, 3), 6, (2, 3)],
         [(1, 3), 6, (1, 4)]]

neighbors = [[(1, 5), 4, (1, 4)], [(1, 3), 6, (1, 4)], [(2, 4), 4, (1, 4)],
             [(0, 4), 6, (1, 4)]]

queue_exists = set(q[0] for q in queue)

for item in neighbors:
    if item[0] in queue_exists:
        print(item)

结果：

[(1, 5), 4, (1, 4)]
[(1, 3), 6, (1, 4)]