Python参数传递的陷阱之从基础类型到类的深入探讨

def greet(name):
    print(f"Hello, {name}!")

def add(a, b):
    a += b
    return a
if __name__ == "__main__":
    # 整数测试
    x, y = 10, 20
    print(add(x, y))  # 输出: 30
    print(x, y)       # 输出: 10 20 (原值不变)
    # 列表测试
    list1, list2 = [1, 2], [3, 4]
    print(add(list1, list2))  # 输出: [1, 2, 3, 4]
    print(list1, list2)       # 输出: [1, 2, 3, 4] [3, 4] (list1被修改)
    # 元组测试
    tuple1, tuple2 = (1, 2), (3, 4)
    print(add(tuple1, tuple2))  # 输出: (1, 2, 3, 4)
    print(tuple1, tuple2)       # 输出: (1, 2) (3, 4) (原值不变)

class Company:
    def __init__(self, name, staffs=[]):  # 危险！默认参数是可变对象
        self.name = name
        self.staffs = staffs
    def add(self, staff):
        self.staffs.append(staff)
    def remove(self, staff):
        if staff in self.staffs:
            self.staffs.remove(staff)
# 测试情况
if __name__ == "__main__":
    # 情况1：传递自定义列表
    staff_list = ["Alice", "Bob"]
    company1 = Company("TechCorp", staff_list)
    company1.add("Charlie")
    print(company1.staffs)  # 输出: ['Alice', 'Bob', 'Charlie']
    print(staff_list)       # 输出: ['Alice', 'Bob', 'Charlie'] (原列表被修改)
    # 情况2：使用默认列表
    company2 = Company("StartUp1")
    company3 = Company("StartUp2")
    company2.add("David")
    print(company2.staffs)  # 输出: ['David']
    print(company3.staffs)  # 输出: ['David'] (company3也被影响了！)

class Company:
    def __init__(self, name, staffs=None):  # 使用None作为默认值
        self.name = name
        self.staffs = staffs if staffs is not None else []  # 每次创建新列表
    # 其他方法保持不变

def update_config(config, new_settings):
    """更新配置参数"""
    config.update(new_settings)
    return config
# 使用示例
global_config = {"timeout": 30, "retries": 3}
new_settings = {"timeout": 60, "cache_size": "1GB"}
updated = update_config(global_config, new_settings)
print(updated)      # 输出: {'timeout': 60, 'retries': 3, 'cache_size': '1GB'}
print(global_config) # 输出: 同上！原配置被修改了

def update_config(config, new_settings):
    """安全更新配置参数"""
    new_config = config.copy()
    new_config.update(new_settings)
    return new_config

def process_data(data):
    """处理数据并添加统计信息"""
    data["stats"] = {
        "mean": sum(data["values"]) / len(data["values"]),
        "max": max(data["values"])
    }
    return data
raw_data = {"values": [10, 20, 30, 40]}
processed = process_data(raw_data)
# raw_data现在也包含stats了，这可能不是我们想要的

def process_data(input_data):
    """安全处理数据"""
    output_data = {
        "original_values": input_data["values"].copy(),
        "stats": {
            "mean": sum(input_data["values"]) / len(input_data["values"]),
            "max": max(input_data["values"])
        }
    }
    return output_data