threading_race_conditions.py

import logging
import threading
import time

class FakeDatabase:
    def __init__(self):
        self.value = 0

    def update(self, name):
        logging.info("Thread %s: starting update", name)
        local_copy = self.value
        local_copy += 1
        time.sleep(0.1)
        self.value = local_copy
        logging.info("Thread %s: finishing update", name)

# class FakeDatabase:
#     def __init__(self):
#         self.value = 0
#         self._lock = threading.Lock()

#     def update(self, name):
#         logging.info("Thread %s: starting update", name)
#         logging.debug("Thread %s about to lock", name)
#         with self._lock:
#             logging.debug("Thread %s has lock", name)
#             local_copy = self.value
#             local_copy += 1
#             time.sleep(0.1)
#             self.value = local_copy
#             logging.debug("Thread %s about to release lock", name)
#         logging.debug("Thread %s after release", name)
#         logging.info("Thread %s: finishing update", name)

format = "%(asctime)s: %(message)s"
logging.basicConfig(format=format, level=logging.INFO,
                    datefmt="%H:%M:%S")

database = FakeDatabase()

logging.info("Testing update. Starting value is %d.", database.value)


threads = []
for index in range(2):
    thread = threading.Thread(target=database.update, args=(index,))
    thread.start()
    threads.append(thread)

for thread in threads:
    thread.join()

logging.info("Testing update. Ending value is %d.", database.value)

https://realpython.com/intro-to-python-threading/