49 lines
938 B
Python
49 lines
938 B
Python
"""
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装饰类的装饰器 - 单例模式 - 一个类只能创建出唯一的对象
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上下文语法：
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__enter__ / __exit__
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"""
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import threading
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from functools import wraps
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def singleton(cls):
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"""单例装饰器"""
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instances = {}
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lock = threading.Lock()
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@wraps(cls)
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def wrapper(*args, **kwargs):
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if cls not in instances:
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with lock:
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if cls not in instances:
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instances[cls] = cls(*args, **kwargs)
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return instances[cls]
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return wrapper
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@singleton
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class President():
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def __init__(self, name, country):
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self.name = name
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self.country = country
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def __str__(self):
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return f'{self.country}: {self.name}'
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def main():
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print(President.__name__)
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p1 = President('特朗普', '美国')
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p2 = President('奥巴马', '美国')
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print(p1 == p2)
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print(p1)
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print(p2)
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if __name__ == '__main__':
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main()
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