前面的答案都可以找到唯一的公共元素，但不能解释列表中重复的项目。如果你想让公共元素在列表中以相同的数字出现，你可以使用下面的一行代码:

l2, common = l2[:], [ e for e in l1 if e in l2 and (l2.pop(l2.index(e)) or True)]

或True部分仅在您希望任何元素求值为False时才需要。

使用Python的集合交集:

>>> list1 = [1,2,3,4,5,6]
>>> list2 = [3, 5, 7, 9]
>>> list(set(list1).intersection(list2))
[3, 5]

我已经制定出了深度交叉口的完整解决方案

def common_items_dict(d1, d2, use_set_for_list_commons=True, use_set_for_dict_key_commons=True, append_empty=False):
    result = {}
    if use_set_for_dict_key_commons:
        shared_keys=list(set(d1.keys()).intersection(d2.keys())) # faster, order not preserved
    else:
        shared_keys=common_items_list(d1.keys(), d2.keys(), use_set_for_list_commons=False)

    for k in  shared_keys:
        v1 = d1[k]
        v2 = d2[k]
        if isinstance(v1, dict) and isinstance(v2, dict):
            result_dict=common_items_dict(v1, v2, use_set_for_list_commons, use_set_for_dict_key_commons, append_empty)
            if len(result_dict)>0 or append_empty:
                result[k] = result_dict 
        elif isinstance(v1, list) and isinstance(v2, list):
            result_list=common_items_list(v1, v2, use_set_for_list_commons, use_set_for_dict_key_commons, append_empty)
            if len(result_list)>0 or append_empty:
                result[k] = result_list 
        elif v1 == v2:
            result[k] = v1
    return result

def common_items_list(d1, d2, use_set_for_list_commons=True, use_set_for_dict_key_commons=True, append_empty=False):
    if use_set_for_list_commons: 
        result_list= list(set(d2).intersection(d1)) # faster, order not preserved, support only simple data types in list values
        return result_list

    result = []
    for v1 in d1: 
        for v2 in d2:
            if isinstance(v1, dict) and isinstance(v2, dict):
                result_dict=common_items_dict(v1, v2, use_set_for_list_commons, use_set_for_dict_key_commons, append_empty)
                if len(result_dict)>0 or append_empty:
                    result.append(result_dict)
            elif isinstance(v1, list) and isinstance(v2, list):
                result_list=common_items_list(v1, v2, use_set_for_list_commons, use_set_for_dict_key_commons, append_empty)
                if len(result_list)>0 or append_empty:
                    result.append(result_list)
            elif v1 == v2:
                result.append(v1)
    return result


def deep_commons(v1,v2, use_set_for_list_commons=True, use_set_for_dict_key_commons=True, append_empty=False):
    """
    deep_commons
     returns intersection of items of dict and list combinations recursively

    this function is a starter function, 
    i.e. if you know that the initial input is always dict then you can use common_items_dict directly
    or if it is a list you can use common_items_list directly

    v1 - dict/list/simple_value
    v2 - dict/list/simple_value
    use_set_for_dict_key_commons - bool - using set is faster, dict key order is not preserved 
    use_set_for_list_commons - bool - using set is faster, list values order not preserved, support only simple data types in list values
    append_empty - bool - if there is a common key, but no common items in value of key , if True it keeps the key with an empty list of dict

    """

    if isinstance(v1, dict) and isinstance(v2, dict):
        return common_items_dict(v1, v2, use_set_for_list_commons, use_set_for_dict_key_commons, append_empty)
    elif isinstance(v1, list) and isinstance(v2, list):
        return common_items_list(v1, v2, use_set_for_list_commons, use_set_for_dict_key_commons, append_empty)
    elif v1 == v2:
        return v1
    else:
        return None


needed_services={'group1':['item1','item2'],'group3':['item1','item2']}
needed_services2={'group1':['item1','item2'],'group3':['item1','item2']}

result=deep_commons(needed_services,needed_services2)

print(result)

使用发电机:

common = (x for x in list1 if x in list2)

这样做的好处是，即使在使用庞大的列表或其他庞大的可迭代对象时，它也会在常数时间内(几乎立即)返回生成器。

例如,

list1 =  list(range(0,10000000))
list2=list(range(1000,20000000))
common = (x for x in list1 if x in list2)

对于list1和list2的这些值，这里的所有其他答案都将花费很长时间。

然后，您可以用

for i in common: print(i)

您还可以使用集合并在一行中获得共性:从其中一个集合中减去包含差异的集合。

A = [1,2,3,4]
B = [2,4,7,8]
commonalities = set(A) - (set(A) - set(B))

list1=[123,324523,5432,311,23]
list2=[2343254,34234,234,322123,123,234,23]
common=[]
def common_elements(list1,list2):
    for x in range(0,len(list1)):
        if list1[x] in list2:
            common.append(list1[x])
            
common_elements(list1,list2)
print(common)