Python几种方式实现单例模式

encoding:utf-8

author = 'zhoupao'
date = '2018/7/7 21:47'

方法一：

使用new方法实现单例模式

class SingleTon(object):
_instance = {}
def new(cls,args,kwargs):
if cls not in cls._instance:
cls._instance[cls]=super(SingleTon,cls).new(cls,args,**kwargs)
#一定要返回
return cls._instance[cls]

class Myclass(SingleTon):
class_val=20

def __init__(self,a):
    self.a=a

if name == 'main':
mycls1=Myclass(1)
mycls2=Myclass(1)
print(mycls1 is mycls2)

方法二：
from functools import wraps

装饰器是以类当做形式参数传递过去

def single_ton(cls):
_instance ={}

@wraps(cls)
def single(*args,**kwargs):
    if cls not in _instance:
        _instance[cls]=cls(*args,**kwargs)
    # 这里也一定要返回
    return _instance[cls]
return single