Python singleton

class Singleton:
    """
    A non-thread-safe helper class to ease implementing singletons.
    This should be used as a decorator -- not a metaclass -- to the
    class that should be a singleton.

    The decorated class can define one `__init__` function that
    takes only the `self` argument. Also, the decorated class cannot be
    inherited from. Other than that, there are no restrictions that apply
    to the decorated class.

    To get the singleton instance, use the `instance` method. Trying
    to use `__call__` will result in a `TypeError` being raised.

    """

    def __init__(self, decorated):
        self._decorated = decorated

    def instance(self):
        """
        Returns the singleton instance. Upon its first call, it creates a
        new instance of the decorated class and calls its `__init__` method.
        On all subsequent calls, the already created instance is returned.

        """
        try:
            return self._instance
        except AttributeError:
            self._instance = self._decorated()
            return self._instance

    def __call__(self):
        raise TypeError('Singletons must be accessed through `instance()`.')

    def __instancecheck__(self, inst):
        return isinstance(inst, self._decorated)

Source: stackoverflow.com

Similar codes

0 vote169 views1 answer
Assert with message python
Python
-1 vote200 views1 answer
Find the range in python
Python
0 vote201 views1 answer
Autopytoexe
Python
0 vote173 views1 answer
Back of list
Python
0 vote219 views1 answer
Decode html python
Python
0 vote139 views2 answers
Python can a imported module get variables from main module
Python
6 votes183 views2 answers
How to limit a command to a permission in discord.py
Python
0 vote187 views1 answer
Global /tmp/pip-req-build-civioau0/opencv/modules/videoio/src/cap_v4l.cpp (587) autosetup_capture_mode_v4l2 VIDEOIO(V4L2:/dev/video0): device is busy
Python
32 votes206 views6 answers
Python Map function
Python
0 vote192 views1 answer
Python datetime now only hour and minute
Python