字符串索引-为什么S[0][0]有效且S[1][1]失败？-Stringindexing-WhyS[0][0]worksandS[1][1]fails?

10  

The answer is that S[0] gives you a string of length 1, which thus necessarily has a character at index 0. S[1] also gives you a string of length 1, but it necessarily does not have a character at index 1. See below:

答案是S [0]给你一个长度为1的字符串,因此必须在索引0处有一个字符.S [1]也会给你一个长度为1的字符串,但它必须在索引1处没有字符。 见下文:

>>> S = "spam"
>>> S[0]
's'
>>> S[0][0]
's'
>>> S[1]
'p'
>>> S[1][0]
'p'
>>> S[1][1]
Traceback (most recent call last):
  File "", line 1, in 
    S[1][1]
IndexError: string index out of range

8  

The first index ([0]) of any string is its first character. Since this results in a one-character string, the first index of that string is the first character, which is itself. You can do [0] as much as you want and stay with the same character.

任何字符串的第一个索引([0])是它的第一个字符。由于这会产生一个字符的字符串,因此该字符串的第一个索引是第一个字符,它本身就是一个字符。您可以根据需要执行[0]并保持相同的角色。

The second index ([1]), however, only exists for a string with at least two characters. If you've already indexed a string to produce a single-character string, [1] will not work.

但是,第二个索引([1])仅适用于包含至少两个字符的字符串。如果您已经将索引编入索引以生成单字符字符串,则[1]将不起作用。

>>> a = 'abcd'
>>> a[0]
'a'
>>> a[0][0]
'a'
>>> a[1]
'b'
>>> a[1][0][0]
'b'
>>> a[1][1]
Traceback (most recent call last):
  File "", line 1, in 
IndexError: string index out of range

0  

A Python String will always have the 0th Position String / 1st Character. Even if we do [0] 100 times, you are always selecting the 1st character of the remaining string. Thus....

Python字符串将始终具有第0个位置字符串/第1个字符。即使我们执行[0] 100次,您也总是选择剩余字符串的第一个字符。从而....

For Programming Languages where array subscripts start with 1, you can similarly do this for the 1st Character.

对于数组下标以1开头的编程语言,您可以类似地为第一个字符执行此操作。