編輯列表中每個第N個項目的值

Question

對列表中的每個第n個值執行算術運算的最Python方法是什麼？例如，如果我開始與列表1：

list1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 

我想1添加到每個第二個項目，這將使：

list2 = [1, 3, 3, 5, 5, 7, 7, 9, 9, 11] 

我已經試過：

list1[::2]+1 

還有：

for x in list1: 
    x=2   
    list2 = list1[::x] + 1 

Answer 1

你可以使用slicing與列表理解如下：

In [26]: list1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 

In [27]: list1[1::2] = [x+1 for x in list1[1::2]] 

In [28]: list1 
Out[28]: [1, 3, 3, 5, 5, 7, 7, 9, 9, 11] 

Answer 2

使用enumerate和list comprehension

>>> list1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
>>> [v+1 if i%2!=0 else v for i,v in enumerate(list1)] 
[1, 3, 3, 5, 5, 7, 7, 9, 9, 11] 

Answer 3

list1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
for i in range(1, len(list1), 2): 
    list1[i] +=1 
print(list1) 

使用我％2似乎不是很有效

Answer 4

numpy允許你使用+=操作帶片：

In [15]: import numpy as np 

In [16]: l = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) 

In [17]: l[1::2] += 1 

In [18]: l 
Out[18]: array([ 1, 3, 3, 5, 5, 7, 7, 9, 9, 11]) 

Answer 5

試試這個：

list1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
for i in range(1,len(list1),2): 
    list1[i] += 1 

Answer 6

您可以創建代表三角洲（itertools.cycle([0, 1])一個迭代，然後添加其內容到您現有的名單。

>>> list1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
>>> [a + b for a,b in zip(list1, itertools.cycle([0,1]))] 
[1, 3, 3, 5, 5, 7, 7, 9, 9, 11] 
>>> 

Answer 7

a = [i for i in range(1,11)] 
#a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
b = [a[i]+1 if i%2==1 else a[i] for i in range(len(a))] 
#b = [1, 3, 3, 5, 5, 7, 7, 9, 9, 11]