Question

I have a list of lists of the form:

my_list=[[1,2, A ],[4,5, B ],[7,8, C ]]

并且,我想总结一下每个清单的第一个要素(1+4+7),以便获得总数。我尝试了以下工作,因为名单的某些内容正在阐明:

new_list = list(zip(*my_list))
print (sum(new_list[0]))

在不使用假肢的情况下这样做的最佳方式是什么?

Answer 1

sum(a[0] for a in my_list)

够了。

Answer 2

假设每个分项都有三个要素,你可以这样做:

sum( a for (a,_,_) in my_list )

Otherwise, do this:

sum( a[0] for a in my_list )

从技术上讲,这些使用堆积在发电机的幌子上,但任何你通过的总和都会最终形成一种或另一种方式。

Answer 3

>>> my_list
[[1, 2,  A ], [4, 5,  B ], [7, 8,  C ]]
>>> sum([a[0] for a in my_list])
12
>>>

Will create a list consisting of the first element of each element in my_list, and sum them.

Answer 4

In [1]: import operator

In [2]: my_list=[[1,2, A ],[4,5, B ],[7,8, C ]]

In [3]: sum(map(operator.itemgetter(0),my_list))
Out[3]: 12

或者使用发电机表达方式:

In [4]: sum(row[0] for row in my_list)
Out[4]: 12

发电机的表述更快捷,更容易读:

In [5]: %timeit sum(map(operator.itemgetter(0),my_list))
1000000 loops, best of 3: 1.52 us per loop

In [6]: %timeit sum(row[0] for row in my_list)
1000000 loops, best of 3: 1.02 us per loop

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