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python
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Singleton mode
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class Foo: pass
def
instance():
   
global inst
   
try:
       
inst
   
except:
       
inst =
Foo
()
   
return inst
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class
Singleton(object):   
   
objs 
= {}
   
def __new__(cls, *args, **kv):
       
if cls in cls.objs:
           
return cls.objs[cls]
       
cls.objs[cls] = object.__new__(cls)
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Singleton mode
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Singleton
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2
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class
Singleton(object):
   
objs 
= {}
   
objs_locker = 
threading.Lock()
   
def __new__(cls, *args, **kv):
       
if cls in cls.objs:
           
return cls.objs[cls]
       
cls.objs_locker.acquire()
       
try:
           
if cls in cls.objs: ## double check
locking
               
return cls.objs[cls]
        &nb


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Amusing Python 2: range/xrange

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sample_tuple = (1,3,"ab")
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