-- coding: utf-8 --

L1 = ['Hello', 'World', 18, 'Apple', None] L2=[s.lower() if isinstance(s,str) else s for s in L1] print(L2)

#2 Created at ... [Delete] [Delete and Lock User]

顶个。

#3 Created at ... [Delete] [Delete and Lock User]

为什么这里的for s in L1要放到最后，而没有else的情况时for放到最后就要报错？

#4 Created at ... [Delete] [Delete and Lock User]

#5 Created at ... [Delete] [Delete and Lock User]

reply for #3 我是这样想的：把这一题分为判断if else和运算for in两部分要先进行判断再进行运算没有else则判断式不完全

#6 Created at ... [Delete] [Delete and Lock User]

说来惭愧，几分钟后才看明白逻辑，用下面的式子得到验证：

L2 = [s if not isinstance(s,str) else  s.lower() for s in L1]

逻辑：

1. 首先for遍历L1中所有项
2. 然后if判断是否是str，是则转换，不是则直接打印。