装饰器

装饰器 decorator
类装饰器

class decorator(object):
    def __init__(self, func):
        self.func = func
    def __call__(self, *args, **kw):
        print 'input:', args, kw
        return self.func(*args, **kw)
@decorator
def square_sum(*args, **kw):
    sum = 0
    for i in args:
        sum += i**2
    for j in kw.values():
        sum += j**2
    return sum
>>> square_sum(3, 4, key=5)
input: (3, 4) {'key': 5}
50

带参数的装饰器

def decorator(*args, **kw):
    text = args
    def _(func):
        def wrapper(*args, **kw):
            print 'text: %s' % text
            print 'input:', args, kw
            return func(*args, **kw)
        return wrapper
    return _
注意：decorator中的(*args, **kw) vs wrapper中的(*args, **kw)

举例（装饰器函数；装饰器类；有参与无参）

https://foofish.net/python-decorator.html
相比函数装饰器，类装饰器具有灵活度大、高内聚、封装性等优点。

class Foo(object):
    def __init__(self, func):
        self._fun = func
    def __call__(self):
        print ('class decorator running')
        self._fun()
        print ('class decorator ending')
@Foo
def bar():
    print ('bar')

bar()

带参数的装饰器

def use_logging(level):
    def decorator(func):
        def wrapper(*args, **kwargs):
            if level == "warn":
                logging.warn("%s is running" % func.__name__)
            elif level == "info":
                logging.info("%s is running" % func.__name__)
            return func(*args)
        return wrapper

    return decorator

@use_logging(level="warn")
def foo(name='foo'):
    print("i am %s" % name)

foo()

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