用索引替换布尔规则中字符串的一部分

def safe_replace(s, index, new_str):
    if 0 <= index < len(s):
        return s[:index] + new_str + s[index + len(new_str):]
    else:
        return s

# 示例
original_str = "Hello, world!"
new_str = "Python"
index = 7
result = safe_replace(original_str, index, new_str)
print(result)  # 输出：Hello, Python!

import re

def regex_replace(s, pattern, new_str):
    return re.sub(pattern, new_str, s)

# 示例
original_str = "Hello, world!"
pattern = r"world"
new_str = "Python"
result = regex_replace(original_str, pattern, new_str)
print(result)  # 输出：Hello, Python!

def efficient_replace(s, index, new_str):
    return s[:index] + new_str + s[index + len(new_str):]

# 示例
original_str = "Hello, world!" * 1000
new_str = "Python"
index = 7
result = efficient_replace(original_str, index, new_str)
print(result[:20])  # 输出：Hello, Python!...