python - 装饰器在它装饰的函数被调用之前运行？

Question

举个例子:

def get_booking(f=None):
    print "Calling get_booking Decorator"
    def wrapper(request, **kwargs):
        booking = _get_booking_from_session(request)
        if booking == None:
            # we don't have a booking in our session.
            return HttpRedirect('/')
        else:
            return f(request=request, booking=booking, **kwargs)
    return wrapper

@get_booking
def do_stuff(request, booking):
    # do stuff here

我遇到的问题是，@get_booking 装饰器 甚至在我调用我正在装饰的函数之前就被调用了。

开始时的输出:

Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
Calling get_booking Decorator
[26/Oct/2008 19:54:04] "GET /onlinebooking/?id=1,2 HTTP/1.1" 302 0
[26/Oct/2008 19:54:05] "GET /onlinebooking/ HTTP/1.1" 200 2300
[26/Oct/2008 19:54:05] "GET /site-media/css/style.css HTTP/1.1" 200 800
[26/Oct/2008 19:54:05] "GET /site-media/css/jquery-ui-themeroller.css HTTP/1.1" 200 25492

此时我什至还没有调用装饰过的函数。

我刚刚开始使用装饰器，所以我可能遗漏了一些东西。

Answer 1

我相信 python 装饰器只是语法糖。

@foo
def bar ():
    pass

和

是一样的

def bar ():
    pass
bar = foo(bar)

如您所见，尽管 bar 尚未调用，但正在调用 foo。这就是为什么您会看到装饰器函数的输出。对于您应用了装饰器的每个函数，您的输出应该包含一行。