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pythonfunctionreferenceself

Is there a generic way for a function to reference itself?


I can access a python function's attribute inside of function itself by below code:

def aa():
    print aa.__name__
    print aa.__hash__
    # other simliar

However, if above aa() function is a template for write other code, say bb(), I have to write:

def bb():
    print bb.__name__
    print bb.__hash__
    # other simliar

Is there a "pointer" similar to the self argument in a class method so I could write code like this?

def whatever():
    print self.__name__
    print self.__hash__
    # other simliar

I searched and found someone said to use the class to solve this problem, but that may be a trouble to redefine all the existing functions. Any suggestions?


Solution

  • There is no generic way for a function to refer to itself. Consider using a decorator instead. If all you want as you indicated was to print information about the function that can be done easily with a decorator:

    from functools import wraps
    def showinfo(f):
        @wraps(f)
        def wrapper(*args, **kwds):
             print(f.__name__, f.__hash__)
             return f(*args, **kwds)
        return wrapper
    
    @showinfo
    def aa():
        pass
    

    If you really do need to reference the function, then just add it to the function arguments:

    def withself(f):
        @wraps(f)
        def wrapper(*args, **kwds):
            return f(f, *args, **kwds)
        return wrapper
    
    @withself
    def aa(self):
          print(self.__name__)
          # etc.
    

    Edit to add alternate decorator:

    You can also write a simpler (and probably faster) decorator that will make the wrapped function work correctly with Python's introspection:

    def bind(f):
        """Decorate function `f` to pass a reference to the function
        as the first argument"""
        return f.__get__(f, type(f))
    
    @bind
    def foo(self, x):
        "This is a bound function!"
        print(self, x)
    
    
    >>> foo(42)
    <function foo at 0x02A46030> 42
    >>> help(foo)
    Help on method foo in module __main__:
    
    foo(self, x) method of builtins.function instance
        This is a bound function!
    

    This leverages Python's descriptor protocol: functions have a __get__ method that is used to create bound methods. The decorator simply uses the existing method to make the function a bound method of itself. It will only work for standalone functions, if you wanted a method to be able to reference itself you would have to do something more like the original solution.