Source code for oso.framework.core.singleton

#
# (c) Copyright IBM Corp. 2025
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Singleton."""




[docs]
class Singleton(type):
    """Singleton metaclass. See: https://stackoverflow.com/a/6798042.

    Attributes
    ----------
    _instances : dict
        The instance.
    """

    _instances = {}

    def __call__(cls, *args, **kwargs):
        """Return a cached instance, or create the instance."""
        if cls not in cls._instances:
            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]