decorator可作用于函数和类，功能有两个：

  • Call proxy
  • Interface proxy

Function Decorator

语法：

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@decorator
def F(arg):
    …

F(99)

效果：

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def F(arg):
    …

F = decorator(F)
F(99)

Call proxy示例：

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def decorator(F):
    # Process function F
    return F

@decorator
def func(): …

Interface proxy示例：

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def decorator(F):
    def wrapper(*args):
        # Use F and args
        # F(*args) calls original function
    return wrapper

@decorator
def func(x, y):
    …

func(6, 7)    # 6, 7 are passed to wrapper's *args

decorator class:

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class decorator:
    def __init__(self, func):
        self.func = func
    def __call__(self, *args):
        # Use self.func and args
        # self.func(*args) calls original function

@decorator
def func(x, y):
    …

func(6, 7)

Class Decorator

语法与function decorator类似

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def decorator(cls):
    class Wrapper:
        def __init__(self, *args):
            self.wrapped = cls(*args)
        def __getattr__(self, name):
            return getattr(self.wrapped, name)
    return Wrapper

@decorator
class C:
    def __init__(self, x, y):
        self.attr = 'spam'

x = C(6, 7)
print(x.attr)

Decorator 参数

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def decorator(A, B):
    # save or use A, B
    def actualDecorator(F):
        # Save or use function F
        # Return a callable: nested def, class with __call__, etc.
        return callable
    return actualDecorator