python单例模式实例解析

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:

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:

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:

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:

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。