python 单例模式

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)