如何在python列表中的每个其他项添加文本？

Question

我有一个列表,如:

mylist = ["1", "2", "3", "4", "5"]

我想为每个其他项添加一些文本,所以它看起来像这样:

mylist = ["1a", "2", "3a", "4", "5a"]

我写了这个,每个项目都适用.如何使其仅适用于所有其他项目？

mylist2 = ["a" + item for item in mylist]

Answer 1

一种方法是这样做:

mylist = ["1", "2", "3", "4", "5"]
res = [x + ('a' if i%2 == 0 else '') for i, x in enumerate(mylist)]

这导致:

['1a', '2', '3a', '4', '5a']

这种方法利用了这样一个事实,即当你除以2时你想要改变的项的索引的余数为1.参见模数

Answer 2

试试这个:

for i in range(0, len(mylist), 2):
    mylist[i] = mylist[i] + "a"

编辑1:

for i in range(0, len(mylist), 2):
    mylist[i] += "a"

Answer 3

使用enumerate和模来用三元数来测试奇数或偶数值.

mylist = ["1", "2", "3", "4", "5"]
mylist2 = [item if i%2 else "a" + item for i,item in enumerate(mylist)]

结果:

>>> mylist2
['a1', '2', 'a3', '4', 'a5']

拿到1a,等...只需切换"a" + item通过item + "a"