Pythonistas

Singleton pattern

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Dominic Yeboah
·

1 min read

The Singleton pattern is used to ensure that a class has only one instance and provides a global access point to that instance. In this example, the Singleton class has a private class attribute __instance that is used to store the instance of the class. The __init__ method checks if an instance has already been created, and if not, it creates one. The getInstance method is a class method that returns the instance of the class.

class Singleton:
    __instance = None

    def __init__(self):
        if not Singleton.__instance:
            print(" __init__ method called..")
        else:
            print("Instance already created:", self.getInstance())

    @classmethod
    def getInstance(cls):
        if not cls.__instance:
            cls.__instance = Singleton()
        return cls.__instance

s = Singleton() # __init__ method called..
print("Object created", Singleton.getInstance()) # Instance already created: <__main__.Singleton object at 0x7f75d9b1fcf8>
s1 = Singleton() # Instance already created: <__main__.Singleton object at 0x7f75d9b1fcf8>
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