inheritance - python error when initializing a class derived from and abstract one -

i have simple code , strange error:

from abc import abcmeta, abstractmethod  class cviterator(abcmeta):      def __init__(self):          self.n = none # value of n obtained in fit method         return   class kfold_new_version(cviterator): # new version of kfold      def __init__(self, k):         assert k > 0, valueerror('cannot have k below 1')         self.k = k         return    cv = kfold_new_version(10)  in [4]: --------------------------------------------------------------------------- typeerror                                 traceback (most recent call last) <ipython-input-4-ec56652b1fdc> in <module>() ----> 1 __pyfile = open('''/tmp/py13196ibs''');exec(compile(__pyfile.read(), '''/home/donbeo/desktop/prova.py''', 'exec'));__pyfile.close()  /home/donbeo/desktop/prova.py in <module>()      19       20  ---> 21 cv = kfold_new_version(10)  typeerror: __new__() missing 2 required positional arguments: 'bases' , 'namespace' 

what doing wrong? theoretical explanation appreciated.

you used abcmeta meta class incorrectly. meta class, not base class. use such.

for python 2, means assigning __metaclass__ attribute on class:

class cviterator(object):     __metaclass__ = abcmeta      def __init__(self):         self.n = none # value of n obtained in fit method 

in python 3, you'd use metaclass=... syntax when defining class:

class cviterator(metaclass=abcmeta):     def __init__(self):         self.n = none # value of n obtained in fit method