不要使用循环，而要使用正则表达式。我建议阅读关于正则的内容，以便更好地理解。
现在，使用以下代码：

import re

def add_deg(string):
    # Create a regular expression to match "a" followed by a number
    pattern = r"a\d"
    # Use re.sub() to replace the first occurrence of the pattern with ")deg" added after the number
    return re.sub(pattern, r"\g<0>)deg", string, count=1)

# Test the function
print(add_deg("abc123def456"))  # Output: "abc123)degdef456"
print(add_deg("abcdef"))  # Output: "abcdef"

参数count=1会将替换次数限制为1。您可以根据需要更改它。
如果有帮助就告诉我。

修改发布以获得预期结果

def add_degree_symbol(string):
    result = ""
    numbers_after_a = False
    for c in string:
        if c == "a":
            numbers_after_a = True
            result += c
        elif numbers_after_a and not c in "0123456789":
            result += "hi" + c
            numbers_after_a = False
        else:
            result += c
    return result

• • 测试**

print(add_degree_symbol("a123b"))  # outputs "a123hib" 
print(add_degree_symbol("a123+456b"))  # outputs "a123hi+456b" 
print(add_degree_symbol("a123*456b"))  # outputs "a123hi*456b" 
print(add_degree_symbol("abcdefghijklmnopqrstuvwxyz"))  # outputs "abcdefghijklmnopqrstuvwxyz" 
print(add_degree_symbol("a1234567890b"))  # outputs "a1234567890hib

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