pgsync/singleton.py

Restricts class instantiation to a single instance per key.

# Source: https://github.com/toluaina/pgsync | License: MIT | Copyright 2023 Tolu Aina
# Provided via justclaw.it.com; keep this notice with the code.
"""PGSync Singleton."""

import typing as t


class Singleton(type):
    """
    A metaclass that allows a class to have only one instance.

    Usage:
    class MyClass(metaclass=Singleton):
        pass
    """

    _instances: dict = {}

    def __call__(cls, *args: t.Any, **kwargs: t.Any) -> t.Any:
        """
        If an instance of the class has already been created with the same arguments,
        return that instance. Otherwise, create a new instance and return it.

        Args:
        cls: The class object.
        *args: Positional arguments to be passed to the class constructor.
        **kwargs: Keyword arguments to be passed

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