How make a singleton using Python?
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我想做一个单音模式：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | class Room: obj = None def __new__(cls): if cls.obj is None: cls.obj = object.__new__(cls) return cls.obj def __init__(self, left_wall, right_wall, front_wall, back_wall): self.left_wall = left_wall self.right_wall = right_wall self.front_wall = front_wall self.back_wall = back_wall def __str__(self): return str(self.left_wall) + str(self.right_wall) + str(self.front_wall) + str(self.back_wall) room_obj = Room(True, False, True, True) print(room_obj) room_obj2 = Room(True, False, False, True) print(room_obj2) print(room_obj is room_obj2) |
运行此代码后，在控制台中获取以下内容：
1 2 3 4 | kalinin@kalinin ~/python/object2 $ python index.py TrueFalseTrueTrue TrueFalseFalseTrue False |
它不应该创建两个对象
您可以在http://python-3-patterns-adilms-test.readthedocs.org/en/latest/singleton.html中尝试这个示例。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | class OnlyOne: class __OnlyOne: def __init__(self, arg): self.val = arg def __str__(self): return repr(self) + self.val instance = None def __init__(self, arg): if not OnlyOne.instance: OnlyOne.instance = OnlyOne.__OnlyOne(arg) else: OnlyOne.instance.val = arg def __getattr__(self, name): return getattr(self.instance, name) |