design_pytterns.singleton package

Singleton class

class design_pytterns.singleton.Singleton(*args: Any, **kwargs: Any)

Bases: object

Class implementation of Singleton-pattern.

This implementation of the Singleton pattern calls the __init__ method of the subclass once, for the initialization of the global instance. In the following calls to the constructor, the __init__ method is not executed, ignoring any argument passed to it and returning the very first created instance instead.

Examples

>>> from design_pytterns.singleton import Singleton
>>>
>>> class MyNumber(Singleton):
...     def __init__(self, number):
...         self.number = number
...     def __str__(self):
...         return self.number
...
>>> test_1 = MyNumber(5)
>>> test_2 = MyNumber()  # No TypeError is raised
>>> test_3 = MyNumber(10)
>>>
>>> id(test_1), test_1
(139703749013216, 5)
>>> id(test_2), test_2
(139703749013216, 5)
>>> id(test_3), test_3
(139703749013216, 5)

SingletonMeta class

class design_pytterns.singleton.SingletonMeta(name: str, bases: Tuple[type, …], mmbs: dict[str, Any])

Bases: type

Metaclass implementation of Singleton-pattern.