| 150 | |
| 151 | |
| 152 | class Singleton(type): |
| 153 | __instances = {} |
| 154 | __lock = threading.Lock() |
| 155 | |
| 156 | class _LockedObj: |
| 157 | def __init__(self, obj, lock): |
| 158 | self.obj = obj |
| 159 | self.lock = lock |
| 160 | |
| 161 | def __call__(cls, *args, **kwargs): |
| 162 | if cls not in cls.__instances: |
| 163 | with cls.__lock: |
| 164 | if cls not in cls.__instances: |
| 165 | cls.__instances[cls] = cls._LockedObj(None, threading.Lock()) |
| 166 | |
| 167 | if not cls.__instances[cls].obj: |
| 168 | with cls.__instances[cls].lock: |
| 169 | if not cls.__instances[cls].obj: |
| 170 | cls.__instances[cls].obj = super(Singleton, cls).__call__(*args, **kwargs) |
| 171 | return cls.__instances[cls].obj |
| 172 | |
| 173 | |
| 174 | def stable_uniq(it): |