# -*- coding: utf-8 -*-
from abc import ABCMeta


class Singleton(type):
    '''
    singleton meta class
    '''
    _instances = {}
    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = \
                super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]


class SingletonABCMeta(ABCMeta):
    '''
    singleton abstract meta class
    '''
    _instances = {}
    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = \
                super(SingletonABCMeta, cls).__call__(*args, **kwargs)
        return cls._instances[cls]
