Python中的扩展切片语法

Question

我正在使用一些字符串和coudn来让自己了解切片是如何工作的， 以下输出＆＃34; i＆＃34;

＆＃34;输入＆＃34; [0 :: - 1]

而以下输出＆＃34; tupni＆＃34;

＆＃34;输入＆＃34; [:: - 1]

我不能得到的是第一个，以及负指数的切片是如何工作的

Answer 1

也许这些例子可以澄清这一点：

In [146]: "input"[::-1] # from back to the begining. Equivalent to: "input"[len("input")::-1]
Out[146]: 'tupni'

In [147]: "input"[0::-1] # from back to the 0'th (i.e. first) element from back
Out[147]: 'i'

In [148]: "input"[1::-1] # from back to the 2ed element from back
Out[148]: 'ni'

In [151]: "input"[len("input")::-1] # from back to the last element from back (alterantive way)
Out[151]: 'tupni'