example/speech_recognition/singleton.py

# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

import logging as log

class Singleton:
    def __init__(self, decrated):
        log.debug("Singleton Init %s" % decrated)
        self._decorated = decrated

    def getInstance(self):
        try:
            return self._instance
        except AttributeError:
            self._instance = self._decorated()
            return self._instance

    def __new__(class_, *args, **kwargs):
        print "__new__"
        class_.instances[class_] = super(Singleton, class_).__new__(class_, *args, **kwargs)
        return class_.instances[class_]

    def __call__(self):
        raise TypeError("Singletons must be accessed through 'getInstance()'")


class SingletonInstane:
  __instance = None

  @classmethod
  def __getInstance(cls):
    return cls.__instance

  @classmethod
  def instance(cls, *args, **kargs):
    cls.__instance = cls(*args, **kargs)
    cls.instance = cls.__getInstance
    return cls.__instance