如何遍历replace()函数python

str.replace(old, new[, count])

def replace_all_instances(text, old, new):
    # 初始化结果字符串
    result = ''
    # 初始化索引
    index = 0
    # 获取原始字符串的长度
    text_length = len(text)
    
    # 遍历字符串
    while index < text_length:
        # 查找子串的位置
        found_index = text.find(old, index)
        if found_index == -1:
            # 如果没有找到更多匹配项，将剩余的字符串添加到结果中并退出循环
            result += text[index:]
            break
        else:
            # 将找到的子串之前的部分添加到结果中
            result += text[index:found_index]
            # 添加替换后的子串
            result += new
            # 更新索引到找到的子串之后
            index = found_index + len(old)
    
    return result

# 示例使用
original_text = "hello world, hello universe"
old_substring = "hello"
new_substring = "hi"

# 替换所有"hello"为"hi"
replaced_text = replace_all_instances(original_text, old_substring, new_substring)
print(replaced_text)  # 输出: "hi world, hi universe"