在Python装饰器中获取类

Question

In this code:

def online_only(func, self):
    def f(*args, **kwargs):
        if self.running:
            return func(*args, **kwargs)
        else:
            return False
    return f
class VM(object):
   @property
   def running(self):
       return True
   @property
   @online_only
   def diskinfo(self):
       return True

I want diskinfo to run only when VM.running returned True. How can I get online_only to be able to read self.running?

Answer 1

self is passed as the first parameter to the wrapping function, so just treat the first parameter specially in f :

def online_only(func):
    def f(self, *args, **kwargs):
        if self.running:
            return func(self, *args, **kwargs)
        else:
            return False
    return f

Answer 2

1. You can not have two arguments in def online_only(func, self) ? it will raise TypeError, so change it to def online_only(func)
2. The first argument to wrapped function would be self, you can just use that eg

---

def online_only(func):
    def f(self):
        if self.running:
            return func(self)
        else:
            return False
    return f

class VM(object):
    @property
    def running(self):
        return True

    @property
    @online_only
    def diskinfo(self):
        return True

print VM().diskinfo