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 vote212 views1 answer
Accessing python dictionary values with dot
Python
4 votes214 views2 answers
Python Program to count the number of lowercase letters and uppercase letters in a string.
Python
1 vote192 views1 answer
How to set required drf serialzier
Python
0 vote199 views1 answer
Falcon 900 price
Python
0 vote191 views1 answer
Run all python files in a directory in bash
Python
0 vote195 views1 answer
Tensorflow matrix multiplication
Python
0 vote209 views1 answer
How to import flask restful using pip
Python
0 vote182 views1 answer
Python utf upper()
Python
0 vote182 views9 answers
Python how to count ever yfile in fodler
Python
4 votes196 views2 answers
Plot distribution seaborn
Python