來自一個列表的兩個總和

Question

我想要列出兩個不同值的總和。例如：

sample = [(1,3), (4,5), (8,2)] 

我想輸出是

13, 10 

我能做到這一點在幾個不同的方式。以下是我目前的方式：

t1 = 0 
t2 = 0 
for item1, item2 in sample: 
    t1 += item1 
    t2 += item2 

什麼是Pythonic更好的解決方法？

Answer 1

你可以試試這個：

from itertools import izip 
sample = [(1,3), (4,5), (8,2)] 
t1, t2 = map(sum, izip(*sample)) 

你也可以用它代替map列表理解。

from itertools import izip 
sample = [(1,3), (4,5), (8,2)] 
t1, t2 = [sum(t) for t in izip(*sample)] 

而且你可以處理兩個以上的總和：

from itertools import izip 
sample = [(1, 3, 1), (4, 5, 1), (8, 2, 1)] 
sums = [sum(t) for t in izip(*sample)] 
# sums == [13, 10, 3] 

Answer 2

sample = [(1,3), (4,5), (8,2)] 

r1 = 0 
r2 = 0 
for v in sample: 
    r1, r2 = r1+v[0], r2+v[1] 

print r1, r2 

雖然@ FastTurtle的是涼爽。

Answer 3

一個班輪：

sum([ x[0] for x in sample ]), sum([ x[1] for x in sample ]) 

還是未知維度的列表：

map(lambda i: sum(x[i] for x in sample), range(len(sample[0]))) 

Answer 4

一個functoinal方法：

from operator import add 
from functools import partial 
sample = [(1,3), (4,5), (8,2)] 
result = reduce(partial(map, add), sample) 

result將列表[13, 10]運行此之後碼。

Answer 5

如果你打算做很多事情（在大數據集上），numpy會有幫助。

>>> from numpy import * 
>>> sample = [(1,3), (4,5), (8,2)] 
>>> sum(array(sample), axis=1) 
array([ 4, 9, 10]) 
>>> sum(array(sample), axis=0) 
array([13, 10])