Mercurial

comparison asyncio_threads/bank_question/main.py @ 48:46daba6e3cf4

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Few python scrtips to show how to use asychio.
author MrJuneJune <me@mrjunejune.com>
date Sat, 13 Dec 2025 14:23:02 -0800
parents
children
comparison
equal deleted inserted replaced
47:829623189a57 48:46daba6e3cf4
1 # # Bank Account
2 #
3 # You are given a simplified multi-threaded “bank account” implementation used by one of our infrastructure teams. The current code processes deposits concurrently but produces incorrect results.
4 #
5 # Task
6 #
7 # Identify the concurrency bugs in the implementation.
8 #
9 # Explain why these bugs occur.
10 #
11 # Fix the implementation without modifying the existing BankAccount class directly.
12 #
13 # You may use subclassing (Python) or embedding (Go-style composition), depending on the language you choose.
14 #
15 # Ensure your solution is thread-safe and produces the correct final balance (1200).
16
17 from threading import Lock
18 from concurrent.futures import ThreadPoolExecutor
19 import time
20
21 class BankAccount:
22 def __init__(self, balance):
23 self.balance = balance
24 self._lock = Lock()
25
26 def deposit(self, amount):
27 while (self._lock.locked()):
28 pass
29 self._lock.acquire()
30 new_balance = self.balance + amount # read
31 time.sleep(0.1) # simulate delay
32 self.balance = new_balance # write
33 self._lock.release()
34
35
36 account = BankAccount(0)
37
38 with ThreadPoolExecutor(max_workers=2) as executor:
39 futures = [
40 executor.submit(account.deposit, 500),
41 executor.submit(account.deposit, 700),
42 ]
43 print(account.balance)