Python 單例模式實現的五種方式

# 全域性變數

ip = '192.168.13.98'
port = '3306'

class mysql:

__instance = none
def __init__(self, ip, port):
self.ip = ip
self.port = port
@classmethod
def instance(cls, *args, **kwargs):
if args or kwargs:
cls.__instance = cls(*args, **kwargs)
return cls.__instance
obj1 = mysql.instance(ip, port)
obj2 = mysql.instance()
obj3 = mysql.instance()
print(obj1)
print(obj2, obj2.__dict__)
print(obj3, obj3.__dict__)

def singlegon(cls):

_instance = cls(ip, port)
if args or kwargs:
return cls(*args, **kwargs)
return _instance
@singlegon
class mysql1:
def __init__(self, ip, port):
self.ip = ip
self.port = port
obj1 = mysql1()
obj2 = mysql1()
obj3 = mysql1('1.1.1.3', 8080)
print(obj1)
print(obj2, obj2.__dict__)
print(obj3, obj3.__dict__)

class mymetaclass(type):

def __init__(self, class_name, class_bases, class_dic):
super().__init__(class_name, class_bases, class_dic)
self.__instance = self(ip, port)
def __call__(self, *args, **kwargs):
if args or kwargs:
obj = self.__new__(self)
self.__init__(obj, *args, **kwargs)
self.__instance = obj
return self.__instance
class mysql2(metaclass=mymetaclass):
def __init__(self, ip, port):
self.ip = ip
self.port = port
obj1 = mysql2()
obj2 = mysql2()
obj3 = mysql2('1.1.1.3', 80)
print(obj1)
print(obj2, obj2.__dict__)
print(obj3, obj3.__dict__)

# instance.py

class mysql:
def __init__(self, ip, port):
self.ip = ip
self.port = port
ip = '192.168.13.98'
port = 3306
instance = mysql(ip, port)
# 測試**
import os, sys
from test import instance
obj1 = instance.instance
obj2 = instance.instance
obj3 = instance.mysql('1.1.1.3', 80)
print(obj1)
print(obj2, obj2.__dict__)
print(obj3, obj3.__dict__)

class mysql3(object):

__instance = none
__first_init = true
def __init__(self, ip, port):
if self.__first_init:
self.ip = ip
self.port = port
self.__first_init = false
def __new__(cls, *args, **kwargs):
if not cls.__instance:
cls.__instance = object.__new__(cls)
return cls.__instance
obj1 = mysql3(ip, port)
obj2 = mysql3(ip, port)
obj3 = mysql3('1.1.1.3', 80)
print(obj1)
print(obj2, obj2.__dict__)
print(obj3, obj3.__dict__)

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