裝飾器是一種修改或增強函數(shù)或類行為而不改變其源代碼的工具。它通過接受目標(biāo)函數(shù)或類作為參數(shù)，并返回一個新的包裝后的函數(shù)或類來實現(xiàn)功能擴展，常用于添加日志、權(quán)限控制、計時等功能。要創(chuàng)建一個裝飾器：1. 定義一個接收函數(shù)或類的函數(shù)；2. 在其中定義包裝函數(shù)以添加額外操作；3. 調(diào)用原始函數(shù)或類；4. 返回包裝后的結(jié)果。使用@decorator_name語法將其應(yīng)用到目標(biāo)函數(shù)或類上即可。對于帶參數(shù)的函數(shù)，可在裝飾器中使用*args和**kwargs確保兼容性。Python內(nèi)置了如@staticmethod、@classmethod和@property等常用裝飾器，第三方庫如Flask也廣泛使用裝飾器進行路由映射。裝飾器適用于需將通用邏輯與核心業(yè)務(wù)分離的場景，但應(yīng)避免過度堆疊復(fù)雜裝飾器，以免影響可讀性和維護性。

Decorators in Python are a way to modify or enhance functions or classes without changing their source code. They’re commonly used to add functionality like logging, access control, timing, and more — all while keeping your code clean and reusable.

What Exactly Is a Decorator?

At its core, a decorator is just a function (or class) that wraps another function or class, modifying its behavior. The key idea is that you pass a function into another function, and the decorator returns a new function that usually does something extra before or after calling the original one.

Here's a basic example:

def my_decorator(func):
    def wrapper():
        print("Before function call")
        func()
        print("After function call")
    return wrapper

@my_decorator
def say_hello():
    print("Hello")

say_hello()

This will output:

Before function call
Hello
After function call

So when you use @my_decorator above say_hello, it’s equivalent to writing:

say_hello = my_decorator(say_hello)

How to Create and Use Function Decorators

Creating your own decorator starts with understanding how functions can be passed around as objects. Here’s how to build a simple one:

1. Define a function that takes another function as an argument.
2. Inside it, define a wrapper function that does something extra.
3. Call the original function inside the wrapper.
4. Return the wrapper function.

You can then apply this decorator using the @decorator_name syntax right above the function definition.

If your decorated function needs arguments, make sure your wrapper handles them. You can use *args and **kwargs for flexibility:

def my_decorator(func):
    def wrapper(*args, **kwargs):
        print("Something before")
        result = func(*args, **kwargs)
        print("Something after")
        return result
    return wrapper

This version works with any function, regardless of what parameters it accepts.

Using Built-in and Third-Party Decorators

Python comes with some handy decorators built in. For example:

• @staticmethod and @classmethod – Used in classes to define methods that don't require instance or class instantiation respectively.
• @property – Makes a method behave like an attribute, useful for computed properties and encapsulation.

Third-party libraries also use decorators heavily. For instance, Flask uses them to map URLs to functions:

@app.route('/')
def home():
    return "Welcome!"

These tools help reduce boilerplate and make your intentions clear without cluttering logic.

When Should You Use Decorators?

Use decorators when you want to separate cross-cutting concerns from your main logic — things like authentication, logging, caching, input validation, etc.

They're especially useful when:

• You need to apply the same behavior to multiple functions.
• You want to keep your core logic clean and readable.
• You're working on frameworks or libraries where extensibility matters.

Just remember: a decorator should ideally do one thing well. If you find yourself stacking many complex decorators, consider refactoring or adding comments so others (or future you) can understand what's going on.

That's basically it. They might seem a bit confusing at first, but once you get the pattern down, they become a powerful part of your Python toolkit.

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