Python3: check if method is static

问题

Simmilar question (related with Python2: Python: check if method is static)

Lets concider following class definition:

class A:
  def f(self):
    return 'this is f'

  @staticmethod
  def g():
    return 'this is g'

In Python 3 there is no instancemethod anymore, everything is function, so the answer related to Python 2 will not work anymore.

As I told, everything is function, so we can call A.f(0), but of course we cannot call A.f() (argument missmatch). But if we make an instance a=A() and we call a.f() Python passes to the function A.f the self as first argument. Calling a.g() prevents from sending it or captures the self - so there have to be a way to test if this is staticmethod or not.

So can we check in Python3 if a method was declared as static or not?

回答1:

class A:
  def f(self):
    return 'this is f'

  @staticmethod
  def g():
    return 'this is g'
print(type(A.__dict__['g']))
print(type(A.g))

<class 'staticmethod'>
<class 'function'>

回答2:

I needed this solution and wrote the following based on the answer from @root

def is_method_static(cls, method_name):
    # http://stackoverflow.com/questions/14187973/python3-check-if-method-is-static
    for c in cls.mro():
        if method_name in c.__dict__:
            return isinstance(c.__dict__[method_name], staticmethod)
    raise RuntimeError("Unable to find %s in %s" % (method_name, cls.__name__))

回答3:

For Python 3.2 or newer, use inspect.getattr_static() to retrieve the attribute without invoking the descriptor protocol:

Retrieve attributes without triggering dynamic lookup via the descriptor protocol, __getattr__() or __getattribute__().

Use isinstance(..., staticmethod) on the result:

>>> from inspect import getattr_static
>>> isinstance(getattr_static(A, 'g'), staticmethod)
True

The function can handle both instances and classes, and will scan the full class hierarchy for you:

>>> class B(A): pass
...
>>> isinstance(getattr_static(B, 'g'), staticmethod)  # inherited
True
>>> isinstance(getattr_static(B(), 'g'), staticmethod)  # instance, inherited
True

来源：https://stackoverflow.com/questions/14187973/python3-check-if-method-is-static