2019-01-25 02:52:40 +08:00
|
|
|
|
"""
|
|
|
|
|
|
装饰类的装饰器 - 单例模式 - 一个类只能创建出唯一的对象
|
|
|
|
|
|
上下文语法：
|
|
|
|
|
|
__enter__ / __exit__
|
|
|
|
|
|
"""
|
|
|
|
|
|
import threading
|
|
|
|
|
|
|
|
|
|
|
|
from functools import wraps
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
def singleton(cls):
|
|
|
|
|
|
"""单例装饰器"""
|
|
|
|
|
|
instances = {}
|
|
|
|
|
|
lock = threading.Lock()
|
|
|
|
|
|
|
|
|
|
|
|
@wraps(cls)
|
|
|
|
|
|
def wrapper(*args, **kwargs):
|
|
|
|
|
|
if cls not in instances:
|
|
|
|
|
|
with lock:
|
|
|
|
|
|
if cls not in instances:
|
|
|
|
|
|
instances[cls] = cls(*args, **kwargs)
|
|
|
|
|
|
return instances[cls]
|
|
|
|
|
|
|
|
|
|
|
|
return wrapper
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
@singleton
|
|
|
|
|
|
class President():
|
|
|
|
|
|
|
|
|
|
|
|
def __init__(self, name, country):
|
|
|
|
|
|
self.name = name
|
|
|
|
|
|
self.country = country
|
|
|
|
|
|
|
|
|
|
|
|
def __str__(self):
|
|
|
|
|
|
return f'{self.country}: {self.name}'
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
def main():
|
|
|
|
|
|
print(President.__name__)
|
|
|
|
|
|
p1 = President('特朗普', '美国')
|
|
|
|
|
|
p2 = President('奥巴马', '美国')
|
|
|
|
|
|
print(p1 == p2)
|
|
|
|
|
|
print(p1)
|
|
|
|
|
|
print(p2)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
if __name__ == '__main__':
|
|
|
|
|
|
main()
|
