单例模式，也叫单子模式，是一种常用的软件设计模式。在应用这个模式时，单例对象的类必须保证只有一个实例存在
用装饰器方式实现单例模式
#!/usr/bin/python
# coding=utf-8
def wrapper(cls):
instances = {}
def inner():
if cls not in instances:
instances[cls] = cls()
return cls
return inner
@wrapper
def Foo():
pass
f1 = Foo()
f2 = Foo()
print(f1 is f2)
用静态方法实现单例模式
#!/usr/bin/python
# coding=utf-8
class ConnectPool:
__instatnce = None
@staticmethod
def get_instance():
if ConnectPool.__instatnce:
return ConnectPool.__instatnce
else:
ConnectPool.__instatnce = ConnectPool()
return ConnectPool.__instatnce
obj1 = ConnectPool.get_instance()
obj2 = ConnectPool.get_instance()
print(obj1 is obj2)