- print '----------------------方法1--------------------------'
- class Singleton(object):
- def __new__(cls, *args, **kw):
- if not hasattr(cls, '_instance'):
- orig = super(Singleton, cls)
- cls._instance = orig.__new__(cls, *args, **kw)
- return cls._instance
-
- class MyClass(Singleton):
- a = 1
-
- one = MyClass()
- two = MyClass()
-
- two.a = 3
- print one.a
- print id(one)
- print id(two)
- print one == two
- print one is two
-
- print '----------------------方法2--------------------------'
- class Borg(object):
- _state = {}
- def __new__(cls, *args, **kw):
- ob = super(Borg, cls).__new__(cls, *args, **kw)
- ob.__dict__ = cls._state
- return ob
-
- class MyClass2(Borg):
- a = 1
-
- one = MyClass2()
- two = MyClass2()
-
- two.a = 3
- print one.a
- print id(one)
- print id(two)
- print one == two
- print one is two
- print id(one.__dict__)
- print id(two.__dict__)
-
- print '----------------------方法3--------------------------'
- class Singleton2(type):
- def __init__(cls, name, bases, dict):
- super(Singleton2, cls).__init__(name, bases, dict)
- cls._instance = None
- def __call__(cls, *args, **kw):
- if cls._instance is None:
- cls._instance = super(Singleton2, cls).__call__(*args, **kw)
- return cls._instance
-
- class MyClass3(object):
- __metaclass__ = Singleton2
-
- one = MyClass3()
- two = MyClass3()
-
- two.a = 3
- print one.a
- print id(one)
- print id(two)
- print one == two
- print one is two
-
- print '----------------------方法4--------------------------'
- def singleton(cls, *args, **kw):
- instances = {}
- def _singleton():
- if cls not in instances:
- instances[cls] = cls(*args, **kw)
- return instances[cls]
- return _singleton
-
- @singleton
- class MyClass4(object):
- a = 1
- def __init__(self, x=0):
- self.x = x
-
- one = MyClass4()
- two = MyClass4()
-
- two.a = 3
- print one.a
- print id(one)
- print id(two)
- print one == two
- print one is two
- one.x = 1
- print one.x
- print two.x
posted @
2016-06-15 19:08
天涯逐梦
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