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

1 vote94 views1 answer
Complete the function digits(n) that returns how many digits the number has.
Python
0 vote108 views1 answer
Load a Dictionary from File in Python Using the Load Function of the pickle Module
Python
11 votes107 views3 answers
Pd.set_option
Python
5 votes103 views3 answers
Convert json to csv
Python
0 vote106 views1 answer
Numpy convert true false to 0 1
Python
0 vote221 views1 answer
Python adx indicator
Python
1 vote103 views2 answers
Flask print to console
Python
1 vote149 views1 answer
Git clone in python to tmp directory
Python
15 votes156 views4 answers
Django python install
Python Django
13 votes107 views6 answers
Character in python
Python