function.py

import types
class Function:
    def __init__(self, func):
        self._func = func
    def __call__(self, *args, **kwargs):
        return self._func(*args, **kwargs)
    def __get__(self, obj, objtype=None):
        "Simulate func_descr_get() in Objects/funcobject.c https://docs.python.org/3/howto/descriptor.html#functions-and-methods"
        if obj is None:
            return self
        else:
            return types.MethodType(self, obj)

class Foo:
   def __init__(self):
       self.foo = 42
   bar = Function(lambda self:
       self.foo ** 2
   )