The OO API allows to create empty enums, i.e. without any values.  However, the functional API does not, as this will result in an IndexError as shown below:In [1]: import enumIn [2]: class X(enum.IntFlag): passIn [3]: Y = enum.IntFlag("Y", [])---------------------------------------------------------------------------IndexError                                Traceback (most recent call last)<ipython-input-3-1fda5945e0b2> in <module>()----> 1 Y = enum.IntFlag("Y", [])~/lib/python3.6/enum.py in __call__(cls, value, names, module, qualname, type, start)    291             return cls.__new__(cls, value)    292         # otherwise, functional API: we're creating a new Enum type--> 293         return cls._create_(value, names, module=module, qualname=qualname, type=type, start=start)    294     295     def __contains__(cls, member):~/lib/python3.6/enum.py in _create_(cls, class_name, names, module, qualname, type, start)    382         if isinstance(names, str):    383             names = names.replace(',', ' ').split()--> 384         if isinstance(names, (tuple, list)) and isinstance(names[0], str):    385             original_names, names = names, []    386             last_values = []IndexError: list index out of range

New changesetdcc8ce44c74492670e6bfbde588a2acbf8f365e0 by ethanfurman (Dong-hee Na) in branch 'master':bpo-30616: Functional API of enum allows to create empty enums. (#2304)https://github.com/python/cpython/commit/dcc8ce44c74492670e6bfbde588a2acbf8f365e0

3.7 fixed, now need 3.6.

New changeset504b95047a8ada06ab630abce55ac2f85566ca37 by ethanfurman (Dong-hee Na) in branch '3.6':[3.6]bpo-30616: Functional API of enum allows to create empty enums. (#2304) (#2324)https://github.com/python/cpython/commit/504b95047a8ada06ab630abce55ac2f85566ca37

Thanks for the bugreport Gerrit Holl and thanks for fixes Dong-hee Na!