singleton

what is it?

a class with only one instance

there are several singletons in python that you use frequently, including None, True, and False

singleton classes aren’t really used as often in python as in other languages. the effect of a singleton is usually better implemented as a global variable inside a module.

creating singleton decorator

import functools
 
# ...
 
def singleton(cls):
    """Make a class a Singleton class (only one instance)"""
    @functools.wraps(cls)
    def wrapper_singleton(*args, **kwargs):
        if wrapper_singleton.instance is None:
            wrapper_singleton.instance = cls(*args, **kwargs)
        return wrapper_singleton.instance
    wrapper_singleton.instance = None
    return wrapper_singleton