代码示例：

def obj_to_str(obj):
    """
    将传递的对象转换为字符串。

    Args:
        obj: 要转换的对象。

    Returns:
        转换后的字符串。
    """
    if isinstance(obj, str):
        return obj
    elif isinstance(obj, (int, float)):
        return str(obj)
    elif isinstance(obj, list):
        return '[{}]'.format(', '.join(obj_to_str(elem) for elem in obj))
    elif isinstance(obj, tuple):
        return '({})'.format(', '.join(obj_to_str(elem) for elem in obj))
    elif isinstance(obj, dict):
        return '{{{}}}'.format(', '.join('{}: {}'.format(obj_to_str(key), obj_to_str(value)) for key, value in obj.items()))
    else:
        return str(obj)

调用示例：

# 字符串
assert obj_to_str("hello world") == "hello world"

# 整数
assert obj_to_str(123) == "123"

# 浮点数
assert obj_to_str(3.1415) == "3.1415"

# 列表
assert obj_to_str([1, "hello", {"key": "value"}, [2, 3]]) == "[1, hello, {key: value}, [2, 3]]"

# 元组
assert obj_to_str((1, "hello", {"key": "value"}, [2, 3])) == "(1, hello, {key: value}, [2, 3])"

# 字典
assert obj_to_str({"key1": "value1", "key2": [1, 2, 3]}) == "{key1: value1, key2: [1, 2, 3]}"

# 自定义类
class Person:
    def __init__(self, name):
        self.name = name
        
    def __str__(self):
        return self.name
    
assert obj_to_str(Person("Rose")) == "Rose"