Python Singleton

singleton.py

"""
    Singleton implementation
"""


class Singleton(type):
    _instances = {}

    def __call__(self, *args, **kwargs):
        if self not in self._instances:
            self._instances[self] = super(Singleton, self).__call__(*args, **kwargs)
        return self._instances[self]

    def __copy__(cls, instance):
        return instance

    @classmethod
    def create(cls, class_object, class_name=None):
        return Singleton(class_name if class_name else class_object.__name__, (class_object,), {})


"""
    Class for singletoning
"""


class RegisterClass(object):
    def __init__(self):
        self.l = []

    def add(self, a):
        self.l.append(a)


"""
    One line creation of singleton
"""

A = Singleton.create(RegisterClass, 'A')
B = Singleton.create(RegisterClass, 'B')

"""
    Operation with singleton
"""

print(A.__name__)
print(B.__name__)

a = A()
a.add(1)

b = B()
b.add(2)

print('a', a.l)
print('b', b.l)

a = A()
a.add(3)

b = B()
b.add(4)

print('a', a.l)
print('b', b.l)

awesome!!!