runonce.py

#original code written as an answer to https://stackoverflow.com/questions/75915644/call-decorator-only-once-in-a-nested-class-function/75915738#75915738

from functools import wraps
from threading import RLock
import contextvars

RUNONCE = contextvars.ContextVar("RUNONCE", default=None)


class RunOnceDecorator:

    def __init__(self, decorator):
        self.decorator = decorator

    def __call__(self, func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            v = RUNONCE.get()
            try:
                if v is None:
                    def mid():
                        # intermediary function needed to set a state on contextvars.context
                        nonlocal result
                        RUNONCE.set(True)
                        result = self.decorator(func,*args, **kwargs)
                    ctx = contextvars.Context()
                    ctx.run(mid)
                else:
                    ctx = None
                    result = func(*args, **kwargs)
            finally:
                del ctx
            return result
        return wrapper


@RunOnceDecorator
def my_decorator(func, self, *args, **kwargs):
    print("before")
    val = func(self, *args, **kwargs)
    print("after")
    return val


pause = 1

class Foo:
    @my_decorator
    def bar(self):
        global pause
        if pause:
            pause = 0
            time.sleep(1)
        print("bar")
        return 0

    @my_decorator
    def baz(self):
        print("baz")
        self.bar()
        return 1

if __name__ == "__main__":
    import threading
    import time
    f1 = Foo()
    #f2 = Foo()
    t1 = threading.Thread(target=f1.bar)
    t2 = threading.Thread(target=f1.baz)
    t1.start()
    time.sleep(0.2)
    t2.start()
    t1.join()
    t2.join()