python - 什么是IndexError？我不断得到它

Question

这是我的代码:

quote = input("Enter a Sentence: ")

a = len(quote)
counter = 0
counter1 = 0
reverse = a

print("The Length of the sentence is",a,"characters long!")

for x in range(0,a):
    if str.isspace(quote[x]) == True:
        counter = counter + 1

print("The Length of the sentence is",a - counter,"characters long (excluding space...)!")

for x in range(0,a):
    if str.isupper(quote[x]) == True:
        counter1 = counter1 + 1

print("The number of Upper Case Characters in the sentence is",counter1,"characters!")

print("The number of Lower Case Characters in the sentence is",a-counter1,"characters long!\n")


while reverse >= 1:
    r = reverse
    print(quote[r])
    r = r - 1

目的是找到有关该句子的所有内容，但唯一的问题是底部的“While”循环。它似乎不起作用，目的是使句子“反”。但是，它给了我一个看起来像这样的错误:

Traceback (most recent call last):
  File "C:\Documents and Settings\ususer\My Documents\Downloads\StringStuff.py", line 27, in <module>
    print(quote[r])
IndexError: string index out of range

我究竟做错了什么？请帮忙!

Answer 1

Python的索引是0，因此字符串的第一个字符是str[0]，最后一个字符是str[len(str) - 1]。因此，由于您以reverse = len(quote)开头，所以最后要执行quote[len(quote)]，它比字符串末尾晚了一个。

因此，您可能应该以reverse = a - 1开头，最后的循环应类似于:

while reverse >= 0:
    print(quote[reverse])
    reverse = reverse - 1