On Sunday, February 1, 2015 at 9:51:11 PM UTC+5:30, Steven D'Aprano wrote: > Rustom Mody wrote: > > > The other day I was taking a class in which I was showing > > - introspection for discovering -- help, type, dir etc at the repl > > - mapping of surface syntax to internals eg. a + b ←→ a.__add__(b) > > > > And a student asked me the diff between > > dir([]) > > and > > [].__dir__() > > > > I didnt know what to say... > > Surely the right answer would have been "I don't know, let's check the > interactive interpreter first, and the docs second." > > Checking the REPL first would have revealed that [].__dir__ raises > AttributeError. In other words, lists don't have a __dir__ method.
?? $ python3 Python 3.4.2 (default, Oct 8 2014, 13:08:17) [GCC 4.9.1] on linux Type "help", "copyright", "credits" or "license" for more information. >>> [].__dir__ <built-in method __dir__ of list object at 0x7f5dd2209f48> >>> dir([]) ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort'] >>> [].__dir__() ['__rmul__', '__str__', '__gt__', 'remove', '__class__', '__getitem__', '__format__', '__ne__', '__sizeof__', '__contains__', '__reduce__', '__add__', 'sort', 'count', 'extend', '__mul__', '__imul__', '__reduce_ex__', '__setitem__', '__doc__', '__ge__', 'copy', '__init__', '__iadd__', '__hash__', '__delitem__', 'insert', '__iter__', '__repr__', '__le__', '__setattr__', 'reverse', '__new__', '__eq__', '__len__', 'index', '__lt__', 'clear', '__subclasshook__', 'append', '__dir__', '__reversed__', '__getattribute__', 'pop', '__delattr__'] >>> What you are describing seems to be true for python2 though -- https://mail.python.org/mailman/listinfo/python-list
