What is the correct way to override the __dir__ method?

inheritance, introspection, python, python-2.7

Solution

Have you tried:

def __dir__(self):
    return sorted(set(
               dir(super(MyRecArray, self)) + \
               self.__dict__.keys() + self.dtype.fields.keys()))

Problem

This question is meant to be more about `__dir__` than about `numpy`. I have a subclass of `numpy.recarray` (in python 2.7, numpy 1.6.2), and I noticed `recarray`'s field names are not listed when `dir`ing the object (and therefore ipython's autocomplete doesn't work). Trying to fix it, I tried overriding `__dir__` in my subclass, like this: ``` def __dir__(self): return sorted(set( super(MyRecArray, self).__dir__() + \ self.__dict__.keys() + self.dtype.fields.keys())) ``` which resulted with: `AttributeError: 'super' object has no attribute '__dir__'`. (I found here this should actually work in python 3.3...) As a workaround, I tried: ``` def __dir__(self): return sorted(set( dir(type(self)) + \ self.__dict__.keys() + self.dtype.fields.keys())) ``` As far as I can tell, this one works, but of course, not as elegantly. Questions: - Is the latter solution correct in my case, i.e. for a subclass of `recarray`? - Is there a way to make it work in the general case? It seems to me it wouldn't work with multiple inheritance (breaking the `super`-call chain), and of course, for objects with no `__dict__`... - Do you know why `recarray` does not support listing its field names to begin with? mere oversight?

Original source