参考了评论区的答案！

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

def trim(s):
    while s[:1]==" ":
        s=s[1:]
    while s[-1:]==" ":
        s=s[:-1]
    return s

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

请问这个while后为什么不能直接写

while s[0]==" ":

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

回楼上，我一开始也没明白，想了一下应该是测试里有一个空的list,没有0号，所以没用

while s[0]==" ":

不知道是不是这样

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

能解释一下这行吗 while s[-1:]==" ":

-1不是最后一个元素吗

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

为什么我用你这个代码运行，总是显示s=[0**:**-1]中间的冒号是invalid syntax？

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

当s=''这个情况，用while s[0]==" ":就会超出index

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

能解释一下这行吗 while s[-1:]==" ":

-1不是最后一个元素吗

这不就和s[:1]引用第一个元素是一个道理吗？