Question

为什么我无法执行此操作？我有2个以下的列表，嵌套和大小不等。我了解到我需要将列表转换为集合（hashable）然后执行比较，但我没有得到比较的输出（比如获取公共元素）我试过下面的方法

list1 = [[u'i2_instance_floating_ip_association'], [u'i1_v1_instance_volume_attach']] 
list2 = [[u'i2_instance_floating_ip_association', u'i2_v1_instance_volume_attach'], [u'i1_instance_floating_ip_association', u'i1_v1_instance_volume_attach']] 
list1 = map(tuple, list1) 
list2 = map(tuple, list2) 
print(set(list1) & set(list2))

提供输出set()

或

for item in list1:
    if item in list2:
       print(item)

什么都没有

fin = [i for i in list1 if i in list2]
print("fin", fin)

给出fin []

Answer 1

问题在于嵌套。你必须一直工作到元素。例如：

for item in list1:
    for list2_item in list2:
        if item[0] in list2_item:
            print(item)

输出：

['i2_instance_floating_ip_association']
['i1_v1_instance_volume_attach']

另一种方法是首先展平两个列表并将它们转换为集合：

flat1 = set(x[0] for x in list1)
flat2 = set(y for x in list2 for y in x)
print(flat1 & flat2)

输出：

{'i1_v1_instance_volume_attach', 'i2_instance_floating_ip_association'}

添加一些打印件以进行调试并了解会发生什么：

for item in list1:
    print('item', item)
    for list2_item in list2:
        print('list2_item', list2_item)
        if item[0] in list2_item:
            print('    found', item[0], 'in', list2_item)
        else:
            print('    did not find', item[0], 'in', list2_item)

输出：

item ['i2_instance_floating_ip_association']
list2_item ['i2_instance_floating_ip_association', 'i2_v1_instance_volume_attach']
    found i2_instance_floating_ip_association in ['i2_instance_floating_ip_association', 'i2_v1_instance_volume_attach']
list2_item ['i1_instance_floating_ip_association', 'i1_v1_instance_volume_attach']
    did not find i2_instance_floating_ip_association in ['i1_instance_floating_ip_association', 'i1_v1_instance_volume_attach']
item ['i1_v1_instance_volume_attach']
list2_item ['i2_instance_floating_ip_association', 'i2_v1_instance_volume_attach']
    did not find i1_v1_instance_volume_attach in ['i2_instance_floating_ip_association', 'i2_v1_instance_volume_attach']
list2_item ['i1_instance_floating_ip_association', 'i1_v1_instance_volume_attach']
    found i1_v1_instance_volume_attach in ['i1_instance_floating_ip_association', 'i1_v1_instance_volume_attach']

嵌套不等列表比较

1 个答案: