python单例模式实例解析

时间:2022-04-09 02:45:09

本文实例为大家分享了python单例模式的具体代码,供大家参考,具体内容如下

多次实例化的结果指向同一个实例

单例模式实现方式

方式一:

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import settings
 
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()
print(obj1)
print(obj2)
print(obj3)

方式二:

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import settings
 
def singleton(cls):
  _instance = cls(settings.IP, settings.PORT)
 
  def wrapper(*args, **kwargs):
    if args or kwargs:
      obj = cls(*args, **kwargs)
      return obj
    return _instance
 
  return wrapper
 
@singleton
class MySQL:
  def __init__(self, ip, port):
    self.ip = ip
    self.port = port
 
obj1 = MySQL()
obj2 = MySQL()
obj3 = MySQL()
print(obj1)
print(obj2)
print(obj3)

方式三:

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import settings
 
class Mymeta(type):
  def __init__(self, class_name, class_bases, class_dic):
    self.__instance = self(settings.IP, settings.PORT)
 
  def __call__(self, *args, **kwargs):
    if args or kwargs:
      obj = self.__new__(self)
      self.__init__(obj, *args, **kwargs)
      return obj
    else:
      return self.__instance
 
class MySQL(metaclass=Mymeta):
  def __init__(self, ip, port):
    self.ip = ip
    self.port = port
 
obj1 = MySQL()
obj2 = MySQL()
obj3 = MySQL()
print(obj1)
print(obj2)
print(obj3)

方式四:

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def f1():
  from singleton import instance
  print(instance)
 
def f2():
  from singleton import instance,MySQL
  print(instance)
  obj = MySQL('1.1.1.1', '3389')
  print(obj)
 
f1()
f2()
 
 
singleton.py文件里内容:
import settings
 
class MySQL:
  print('run...')
 
  def __init__(self, ip, port):
    self.ip = ip
    self.port = port
 
instance = MySQL(settings.IP, settings.PORT)

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:https://www.cnblogs.com/hades0607/archive/2018/08/28/9548684.html