from inspect import getmro

_sentinel = object()
def getattr_static(obj, attr, default=_sentinel):
    """Retrieve attributes without triggering dynamic lookup via the
       descriptor protocol,  __getattr__ or __getattribute__.

       Note: this function may not be able to retrieve all attributes
       reported by dir(obj) and can return descriptors instead of
       instance members in some cases. See the documentation for
       details.
    """
    try:
        instance_dict = object.__getattribute__(obj, "__dict__")
    except AttributeError:
        # C types may not have a __dict__ or a __slots__
        slots = getattr(obj, '__slots__', _sentinel)
        if slots is not _sentinel and attr in slots:
            try:
                # attempt to fetch the slot, we could use type(obj)
                # here, which would bypass __class__ proxying, but
                # we use obj.__class__ elsewhere *anyway* and
                # better to have consistent behaviour for objects
                # that lie about __class__
                desc = getattr_static(obj.__class__, attr)
            except AttributeError:
                # this code path is only possible if __slots__ has
                # been tampered with, harmless anyway
                pass
            else:
                try:
                    return desc.__get__(obj)
                except AttributeError:
                    # arguably incorrect - as the instance member is
                    # not set on this object
                    return desc
    else:
        if attr in instance_dict:
            return instance_dict[attr]

    if not isinstance(obj, type):
        klass = obj.__class__
    else:
        klass = obj
    for entry in getmro(klass):
        try:
            return entry.__dict__[attr]
        except KeyError:
            pass
    if obj is klass:
        # for types we check the metaclass too
        for entry in getmro(type(klass)):
            try:
                return entry.__dict__[attr]
            except KeyError:
                pass
    if default is not _sentinel:
        return default
    raise AttributeError(attr)