Python single-instance mode

Method One

Python code

2. Import threading
6. Class Singleton (object):
8. __instance = None
12. __lock = Threading. Lock () # used to synchronize code
16. def __init__ (self):
18. "Disable the __init__ method"
22. @staticmethod
24. def getinstance ():
26. if not singleton.__instance:
28. Singleton.__lock.acquire ()
30. if not singleton.__instance:
32. Singleton.__instance = object.__new__ (Singleton)
34. object.__init__ (singleton.__instance)
36. Singleton.__lock.release ()
38. return singleton.__instance

1. Disable the __init__ method, and you cannot create objects directly.

2.__instance, privatization of single-instance objects.

[email protected], static method, directly called through the class name.

4.__lock, code lock.

5. Inherit the object class, create a singleton object by calling the __new__ method of object, and then call the __init__ method of object to complete the initialization.

6. Double check lock, both to achieve thread safety and performance is not greatly affected.

Method Two: Use decorator

Python code

2. #encoding =utf-8
4. Def Singleton (CLS):
6. instances = {}
8. def getinstance ():
10. if cls not in instances:
12. instances[CLS] = cls ()
14. return instances[CLS]
16. return getinstance
20. @singleton
22. Class Singletonclass:
24. Pass
28. if __name__ = = ' __main__ ':
30. s = Singletonclass ()
32. S2 = Singletonclass ()
34. Print S
36. Print S2

You should also add thread safety

Attached: Performance no method one high

Python code

2. Import threading
6. Class Sing (object):
8. def __init__ ():
10. "Disable the __init__ method"
14. __inst = None # make it so-called private
18. __lock = Threading. Lock () # used to synchronize code
22. @staticmethod
24. def getinst ():
26. Sing.__lock.acquire ()
28. if not sing.__inst:
30. Sing.__inst = object.__new__ (Sing)
32. object.__init__ (Sing.__inst)
34. Sing.__lock.release ()
36. return Sing.__inst

Python single-instance mode