编写字符串交替大写程序时遇IndexError报错求助

Hey there! Let's get that code working properly. The IndexError: string index out of range you're seeing is caused by a small mistake in your loop range, plus a tiny issue with your initial string value. Let's break it down step by step:

What's Going Wrong? #

1. Incorrect Loop Range: You're using range(0, lenght+1) for your loop. Since Python strings are zero-indexed (meaning the first character is at index 0, the last at len(str1)-1), when i reaches lenght (the full length of your input string), str1[i] doesn't exist—hence the index out of range error.
2. Unwanted Leading Space: Your str2 starts with a space (" "), which will add an extra space at the beginning of your final output.
3. Minor Typo: You wrote lenght instead of length—it's not breaking the code, but fixing it makes things more readable.

Corrected Code #

Here's the fixed version with explanations:

str1 = input("Enter a string: ")
length = len(str1)  # Fixed the typo here
print("Original string =", str1, "\nOriginal string length =", length)
str2 = ""  # Initialize as empty string instead of a space
for i in range(length):  # Loop only through valid indices (0 to length-1)
    if i % 2 == 0:
        str2 += str1[i].upper()
    else:
        str2 += str1[i].lower()  # Ensures odd-indexed chars are lowercase, matching your example
print(str2)

Key Changes Made: #

• Adjusted the loop range to range(length): This keeps us within the valid index bounds of the input string
• Removed the leading space from str2's initial value to clean up the output
• Added .lower() to the else clause: This guarantees odd-positioned characters are lowercase, even if the input has uppercase letters, perfectly matching your school → ScHoOl example

Testing with Your Example #

If you input school, the code will output ScHoOl exactly as you wanted!

内容的提问来源于stack exchange，提问作者Kc Crazy