Python中单例模式总结

class Sigletion(objects):
  import time
  def __init__(self):
    time.sleep(1)
  @classmethod
  def instance(cls,*args,**kwargs)
    if not hasattr(Sigletion,'_instance'):
      Sigletion._instance=Sigletion(*args,**kwargs)
    return Sigletion._instance

import threading

daf task(arg):
  obj=Sigletion.instance()
  print(obj)

for i in range(10):
  t=threading.Thread(target=task,args=[i,])
  t.start()

import time
import threading
class Singleton(object):
  _instance_lock=threading.Lock()
  def __init__(self):
    pass
  def __new__(cls, *args, **kwargs):
    if not hasattr(Singleton,"_instance"):
      with Singleton._instance_lock:
        if not hasattr(Singleton,"_instance"):
          Singleton._instance=object.__new__(cls,*args,**kwargs)
    return Singleton._instance

obj1=Singleton()
obj2=Singleton()
print(obj1,obj2)

def task(arg):
  obj = Singleton()
  print(obj)

for i in range(10):
  t = threading.Thread(target=task,args=[i,])
  t.start()

# 第0步: 执行type的 __init__ 方法【类是type的对象】
class Foo:
  def __init__(self):
    pass

  def __call__(self, *args, **kwargs):
    pass

# 第1步: 执行type的 __call__ 方法
#    1.1 调用 Foo类（是type的对象）的 __new__方法，用于创建对象。
#    1.2 调用 Foo类（是type的对象）的 __init__方法，用于对对象初始化。
obj = Foo()
# 第2步：执行Foodef __call__ 方法
obj()
"""

import threading

class SingletonType(type):
  _instace_lock=threading.Lock()
  def __call__(cls, *args, **kwargs):
    if not hasattr(cls, "_instance"):
      with SingletonType._instace_lock:
        if not hasattr(cls, "_instance"):
          cls._instance = super(SingletonType,cls).__call__(*args, **kwargs)
    return cls._instance
class Foo(metaclass=SingletonType):
  def __init__(self,name):
    self.name=name


obj1 = Foo('name')
obj2 = Foo('name')
print(obj1,obj2)