list(dict.items()) atomic or not

gistfile1.txt

import threading

def one(obj):
    while True:
        skip = set()
        try:
            {k: v for k, v in obj.__dict__.items() if k not in skip}
        except RuntimeError as err:
            print("%s" % err)

def one_proposed_protected(obj):
    while True:
        skip = set()
        try:
            {k: v for k, v in list(obj.__dict__.items()) if k not in skip}
        except RuntimeError as err:
            print("%s" % err)


def two(obj):
    while True:
        obj.foo = 'bar'
        del obj.foo

class Thing:
    def __init__(self):
        self.__dict__.update(
            {letter: value for value, letter in enumerate("abcdefghijklmnop")}
        )

thing = Thing()
t2 = threading.Thread(target=two, args=(thing, ))
t2.start()

# bug in Python 3.8 - no bug in Python 3.10 (dont have 3.9 installed here)
# interestingly, doesn't raise in py2 either
t1 = threading.Thread(target=one, args=(thing, ))

# seems to resolve
# t1 = threading.Thread(target=one_proposed_protected, args=(thing, ))

t1.start()


t1.join()
t2.join()