即使不在列表中，也可以在Python中正确获取重复项

def find_duplicates(lst):
    duplicates = []
    for item in lst:
        if lst.count(item) > 1 and item not in duplicates:
            duplicates.append(item)
    return duplicates

# 示例用法
my_list = [1, 2, 3, 4, 2, 5, 6, 3, 7, 8, 4]
result = find_duplicates(my_list)
print(result)  # 输出: [2, 3, 4]

def find_duplicates(lst):
    return list(set([x for x in lst if lst.count(x) > 1]))

# 示例用法
my_list = [1, 2, 3, 4, 2, 5, 6, 3, 7, 8, 4]
result = find_duplicates(my_list)
print(result)  # 输出: [2, 3, 4]