Scoped decorator

run_once.py

from functools import wraps

SENTINEL = object()


def run_once(func):
    """Decorator which ensures that a function is only executed a single time."""

    class Scope:
        locals = {"result": SENTINEL}

        @staticmethod
        @wraps(func)
        def wrapper(*args, **kwargs):
            if Scope.locals["result"] is SENTINEL:
                Scope.locals["result"] = func(*args, **kwargs)
            return Scope.locals["result"]

    Scope.wrapper.__scope__ = Scope.locals  # so I can overwrite at runtime
    return Scope.wrapper