python singleton

singleton.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

import threading

class KbTerms(object):
    """singleton
    """
    _instance_lock = threading.Lock()

    @staticmethod
    def instance():
        if not hasattr(KbTerms, "_instance"):
            with KbTerms._instance_lock:
                if not hasattr(KbTerms, "_instance"):
                    setattr(KbTerms, "_instance", KbTerms())

        return getattr(KbTerms, "_instance")