python – Calling class staticmethod within the class body?

python – Calling class staticmethod within the class body?

staticmethod objects apparently have a __func__ attribute storing the original raw function (makes sense that they had to). So this will work:

class Klass(object):

    @staticmethod  # use as decorator
    def stat_func():
        return 42

    _ANS = stat_func.__func__()  # call the staticmethod

    def method(self):
        ret = Klass.stat_func()
        return ret

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As an aside, though I suspected that a staticmethod object had some sort of attribute storing the original function, I had no idea of the specifics. In the spirit of teaching someone to fish rather than giving them a fish, this is what I did to investigate and find that out (a C&P from my Python session):

>>> class Foo(object):
...     @staticmethod
...     def foo():
...         return 3
...     global z
...     z = foo

>>> z
<staticmethod object at 0x0000000002E40558>
>>> Foo.foo
<function foo at 0x0000000002E3CBA8>
>>> dir(z)
[__class__, __delattr__, __doc__, __format__, __func__, __get__, __getattribute__, __hash__, __init__, __new__, __reduce__, __reduce_ex__, __repr__, __setattr__, __sizeof__, __str__, __subclasshook__]
>>> z.__func__
<function foo at 0x0000000002E3CBA8>

Similar sorts of digging in an interactive session (dir is very helpful) can often solve these sorts of question very quickly.

This is the way I prefer:

class Klass(object):

    @staticmethod
    def stat_func():
        return 42

    _ANS = stat_func.__func__()

    def method(self):
        return self.__class__.stat_func() + self.__class__._ANS

I prefer this solution to Klass.stat_func, because of the DRY principle.
Reminds me of the reason why there is a new super() in Python 3 🙂

But I agree with the others, usually the best choice is to define a module level function.

For instance with @staticmethod function, the recursion might not look very good (You would need to break DRY principle by calling Klass.stat_func inside Klass.stat_func). Thats because you dont have reference to self inside static method.
With module level function, everything will look OK.

python – Calling class staticmethod within the class body?

What about injecting the class attribute after the class definition?

class Klass(object):

    @staticmethod  # use as decorator
    def stat_func():
        return 42

    def method(self):
        ret = Klass.stat_func()
        return ret

Klass._ANS = Klass.stat_func()  # inject the class attribute with static method value