在settings文件中
IP='1.1.1.1'
PORT=3306
import settings
一:
class MySQL:
__instance=None
def __init__(self, ip, port):
self.ip = ip
self.port = port
@classmethod
def from_conf(cls):
if cls.__instance is None:
cls.__instance=cls(settings.IP, settings.PORT)
return cls.__instance
obj1=MySQL.from_conf()
obj2=MySQL.from_conf()
obj3=MySQL.from_conf()
# obj4=MySQL('1.1.1.3',3302)
print(obj1)
print(obj2)
print(obj3)
# print(obj4)
'''
二:
import settings
def singleton(cls):
_instance=cls(settings.IP,settings.PORT)
def wrapper(*args,**kwargs):
if len(args) !=0 or len(kwargs) !=0:
obj=cls(*args,**kwargs)
return obj
return _instance
return wrapper
@singleton #MySQL=singleton(MySQL) #MySQL=wrapper
class MySQL:
def __init__(self, ip, port):
self.ip = ip
self.port = port
# obj=MySQL('1.1.1.1',3306) #obj=wrapper('1.1.1.1',3306)
# print(obj.__dict__)
obj1=MySQL() #wrapper()
obj2=MySQL() #wrapper()
obj3=MySQL() #wrapper()
obj4=MySQL('1.1.1.3',3302) #wrapper('1.1.1.3',3302)
print(obj1)
print(obj2)
print(obj3)
print(obj4)
'''
三:
import settings
class Mymeta(type):
def __init__(self,class_name,class_bases,class_dic):
#self=MySQL这个类
self.__instance=self(settings.IP,settings.PORT)
def __call__(self, *args, **kwargs):
# self=MySQL这个类
if len(args) != 0 or len(kwargs) != 0:
obj=self.__new__(self)
self.__init__(obj,*args, **kwargs)
return obj
else:
return self.__instance
class MySQL(metaclass=Mymeta): #MySQL=Mymeta(...)
def __init__(self, ip, port):
self.ip = ip
self.port = port
obj1=MySQL()
obj2=MySQL()
obj3=MySQL()
obj4=MySQL('1.1.1.3',3302)
print(obj1)
print(obj2)
print(obj3)
print(obj4)
'''
四:
在singleton文件中import settings
class MySQL:
print('run....')
def __init__(self, ip, port):
self.ip = ip
self.port = port
instance=MySQL(settings.IP,settings.PORT)
在test文件中
def f1():
from singleton import instance
print(instance)
def f2():
from singleton import instance,My
SQL
print(instance)
obj=MySQL('1.1.1.3',3302)
print(obj)
f1()
f2()