如何比较python中的列表/集合列表?
问题描述
比较两个列表/集合并输出差异的最简单方法是什么?是否有任何内置函数可以帮助我比较嵌套列表/集合?
What is the easiest way to compare the 2 lists/sets and output the differences? Are there any built in functions that will help me compare nested lists/sets?
输入:
First_list = [['Test.doc', '1a1a1a', 1111],
['Test2.doc', '2b2b2b', 2222],
['Test3.doc', '3c3c3c', 3333]
]
Secnd_list = [['Test.doc', '1a1a1a', 1111],
['Test2.doc', '2b2b2b', 2222],
['Test3.doc', '8p8p8p', 9999],
['Test4.doc', '4d4d4d', 4444]]
预期输出:
Differences = [['Test3.doc', '3c3c3c', 3333],
['Test3.doc', '8p8p8p', 9999],
['Test4.doc', '4d4d4d', 4444]]
解决方案
所以你想要两个项目列表之间的差异.
So you want the difference between two lists of items.
first_list = [['Test.doc', '1a1a1a', 1111],
['Test2.doc', '2b2b2b', 2222],
['Test3.doc', '3c3c3c', 3333]]
secnd_list = [['Test.doc', '1a1a1a', 1111],
['Test2.doc', '2b2b2b', 2222],
['Test3.doc', '8p8p8p', 9999],
['Test4.doc', '4d4d4d', 4444]]
首先,我将每个列表列表转换为元组列表,因为元组是可散列的(列表不是),因此您可以将元组列表转换为一组元组:
First I'd turn each list of lists into a list of tuples, so as tuples are hashable (lists are not) so you can convert your list of tuples into a set of tuples:
first_tuple_list = [tuple(lst) for lst in first_list]
secnd_tuple_list = [tuple(lst) for lst in secnd_list]
然后你就可以做套路了:
Then you can make sets:
first_set = set(first_tuple_list)
secnd_set = set(secnd_tuple_list)
编辑(由 sdolan 建议):您可以为单行中的每个列表完成最后两个步骤:
EDIT (suggested by sdolan): You could have done the last two steps for each list in a one-liner:
first_set = set(map(tuple, first_list))
secnd_set = set(map(tuple, secnd_list))
注意:map
是一个函数式编程命令,它将第一个参数中的函数(在本例中为 tuple
函数)应用于第二个参数中的每个项目(即在我们的例子中是一个列表的列表).
Note: map
is a functional programming command that applies the function in the first argument (in this case the tuple
function) to each item in the second argument (which in our case is a list of lists).
并找出集合之间的对称差:
and find the symmetric difference between the sets:
>>> first_set.symmetric_difference(secnd_set)
set([('Test3.doc', '3c3c3c', 3333),
('Test3.doc', '8p8p8p', 9999),
('Test4.doc', '4d4d4d', 4444)])
注意 first_set ^ secnd_set
等价于 symmetric_difference
.
此外,如果您不想使用集合(例如,使用 python 2.2),它也很简单.例如,使用列表推导:
Also if you don't want to use sets (e.g., using python 2.2), its quite straightforward to do. E.g., with list comprehensions:
>>> [x for x in first_list if x not in secnd_list] + [x for x in secnd_list if x not in first_list]
[['Test3.doc', '3c3c3c', 3333],
['Test3.doc', '8p8p8p', 9999],
['Test4.doc', '4d4d4d', 4444]]
或使用功能性 filter
命令和 lambda
函数.(你必须测试两种方式并结合起来).
or with the functional filter
command and lambda
functions. (You have to test both ways and combine).
>>> filter(lambda x: x not in secnd_list, first_list) + filter(lambda x: x not in first_list, secnd_list)
[['Test3.doc', '3c3c3c', 3333],
['Test3.doc', '8p8p8p', 9999],
['Test4.doc', '4d4d4d', 4444]]
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