嵌套不等列表比较

Question

为什么我无法执行此操作？我有2个以下的列表，嵌套和不相等的大小。我了解到，我需要列表转换为集（哈希的），然后进行比较，但我不明白的比较的输出（如获得共同的元素） 我尝试下面的方法

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)) 

给输出set()

或

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

给出什么

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

给出fin []

Answer 1

问题是嵌套。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'] 

另一种方法是首先拼合两份名单，并将其转换成集：

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'} 

加一些打印的调试和学习会发生什么：

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']