feat: python
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heyong.fu
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# 反射（Reflection）是指在程序运行时检查、访问和修改其自身状态和行为的能力。Python 作为一种高度动态的语言，天然支持强大的反射机制。
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# 2.核心价值
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# 动态性：在运行时操作对象
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# 灵活性：根据条件动态调用方法
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# 通用性：编写可重用的通用代码
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# 内省：检查对象的结构和能力
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# 核心函数
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# 函数 描述 返回值
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# hasattr(obj, name) 检查对象是否有指定属性 布尔值
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# getattr(obj, name[, default]) 获取对象属性值 属性值或默认值
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# setattr(obj, name, value) 设置对象属性值 None
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# delattr(obj, name) 删除对象属性 None
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# dir(obj) 获取对象所有属性和方法 列表
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# 基本用法
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class Example:
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def __init__(self):
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self.value = 42
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example = Example()
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# 检查属性是否存在
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print(hasattr(example, "value")) # True
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# 获取某个属性值
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print(getattr(example, "value")) # 42
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# 设置新属性
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setattr(example, "new_attr", 100)
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print(getattr(example, "new_attr")) # 100
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# 删除属性
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delattr(example, "new_attr")
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print("new_attr" in dir(example)) # False
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print(dir(example))
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# 安全属性访问
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class Config:
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def __init__(self):
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self.host = "localhost"
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self.port = "8080"
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config = Config()
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timeout = getattr(config, "timeout", 300) # 如果不存在设置默认值
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print(timeout) # 返回默认值
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print("timeout" in dir(config)) # False 不会设置上去
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# 内省函数
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# 4.1.类型检查函数
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# 函数 描述 示例
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# type(obj) 返回对象类型 type(123) → <class 'int'>
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# isinstance(obj, class) 检查对象是否为指定类型 isinstance(123, int) → True
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# issubclass(cls, class) 检查类继承关系 issubclass(Bar, Foo) → True
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# 对象信息函数
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# 函数 描述 示例
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# dir(obj) 获取对象所有属性和方法 dir(obj) → ['attr1', 'method1', ...]
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# vars(obj) 获取对象的属性字典 vars(obj) → {'attr1': 'value1'}
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# obj.__dict__ 对象的属性字典 obj.__dict__ → {'attr1': 'value1'}
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# 示例
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class Foo:
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def __init__(self):
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self.attr1 = "hello"
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class Bar(Foo):
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def method1(self):
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return "world"
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foo = Foo()
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bar = Bar()
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# 类型
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print(type(foo)) # <class '__main__.Foo'>
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print(isinstance(bar, Foo)) # True
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print(issubclass(Bar, Foo)) # True
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# 对象信息
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print(hasattr(foo, "attr1")) # True
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print(getattr(foo, "attr1")) # hello
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print(vars(foo)) # {'attr1': 'hello'}
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print(vars(bar)) # {'attr1': 'hello'}
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print(
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dir(foo)
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) # ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getstate__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'attr1']
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def show_object_members(obj):
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print(f"对象类型: {type(obj)}")
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for attr in dir(obj):
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if attr.startswith("_"):
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continue
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value = getattr(obj, attr)
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if callable(value):
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print(f"[方法] {attr}()")
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else:
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print(f"[属性] {attr} = {value}")
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# 使用示例
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show_object_members(123)
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# 类级别反射是指直接作用于类本身的反射操作，可以：
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# 动态获取和修改类属性（包括类变量）
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# 调用类方法和静态方法
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# 检查类中的方法和属性是否存在
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# 动态给类添加属性或方法
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class DatabaseModel:
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table_name = "users"
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connection_string = "sqlite:///database.bd"
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def __init__(self, id, name):
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self.id = id
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self.name = name
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# @classmethod 装饰器可以将方法包装成类方法，类方法直接通过类来调用，不需要创建实例
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@classmethod
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def get_table_info(cls):
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return f"表名：{cls.table_name},连接{cls.connection_string}"
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# @staticmethod 将方法变为静态方法。静态方法既可以通过类来调用，也可以通过实例来调用，但他们并不会接受任何饮食的第一参数（既不接受类对象，也不接受实例对象）
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@staticmethod
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def validata_data(data):
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return isinstance(data, dict)
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def save(self):
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return f"保存{self.name}到数据库中"
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# 类级别的反射操作
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print(getattr(DatabaseModel, "table_name"))
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print(getattr(DatabaseModel, "connection_string"))
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# 动态修改属性
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setattr(DatabaseModel, "table_name", "customers")
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print(getattr(DatabaseModel, "table_name")) # customers
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# 调用类的方法
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class_method = getattr(DatabaseModel, "get_table_info")
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print(class_method())
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# 调用静态方法
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static_method = getattr(DatabaseModel, "validata_data")
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print(static_method({"key": "val"})) # True
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# 检查类成员
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print(hasattr(DatabaseModel, "table_name")) # True
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print(hasattr(DatabaseModel, "connection_string")) # True
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print(hasattr(DatabaseModel, "get_table_info")) # True
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# 模块级别反射
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# 7.1.概念
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# 模块级反射是指在运行时动态地检查、导入、操作模块及其内容的能力。它可以帮助我们开发出高度可配置、插件化、支持热加载的系统。
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# 7.2.常用函数
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# 函数 描述 示例
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# importlib.import_module(name) 按名称动态导入模块 importlib.import_module("math")
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# getattr(module, name[, default]) 动态获取模块中的函数、类、变量 getattr(math, "sqrt")
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# hasattr(module, name) 判断模块是否有某个属性 hasattr(math, "pow")
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# dir(module) 获取模块内定义的名称列表 dir(math)
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# importlib.reload(module) 重新加载已加载的模块 importlib.reload(math)
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# 基本示例
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import importlib
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from typing import Any
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# 动态导入模块
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module_name = "math"
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math_mod = importlib.import_module(module_name)
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print(
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math_mod
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) # <module 'math' from '/opt/homebrew/Cellar/python@3.12/3.12.3/Frameworks/Python.framework/Versions/3.12/lib/python3.12/lib-dynload/math.cpython-312-darwin.so'>
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print(getattr(math_mod, "sqrt")(16)) # 4.0
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# 检查是否存在某属性
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if hasattr(math_mod, "pow"):
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print(math_mod.pow(2, 8)) # 256.0
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# 应用场景
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# 配置系统
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class ConfigManager:
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def __init__(self, config_dict=None):
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self._config = config_dict or {}
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self._defaultConfig = {
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"debug": False,
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"host": "localhost",
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"port": 8080,
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"timeout": 30,
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}
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def __getattr__(self, name):
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if name in self._config:
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return self._config.get(name)
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elif name in self._defaultConfig:
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return self._defaultConfig.get(name)
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else:
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raise ArithmeticError(f"配置选项不存在{name}")
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def set_config(self, **kwargs):
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for key, val in kwargs.items():
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self._config[key] = val
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def show_config(self):
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all_config = {**self._defaultConfig, **self._config}
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for key, val in all_config.items():
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source = "默认" if key in self._defaultConfig else "自定义"
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print(f"{key}:{val}[{source}]")
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config = ConfigManager()
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print(f"Host: {config.host}") # localhost
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print(f"Port: {config.port}") # 8080
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print(f"Debug: {config.debug}") # False
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config.set_config(host="127.0.0.1", port=9000, new_setting="custom")
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print("\n所有配置:")
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config.show_config()
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requests = [
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("GET", "/users"),
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("GET", "/users/123"),
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("POST", "/users", {"name": "Alice", "email": "alice@example.com"}),
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("PUT", "/users/123", {"name": "Alice Smith"}),
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("DELETE", "/users/123"),
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]
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# *args 会返回一个list
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for method, path, *args in requests:
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params = args[0] if args else {}
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