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annotate asyncio_threads/bank_question/main.py @ 104:2301aeb7503b

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author June Park <parkjune1995@gmail.com>
date Sat, 03 Jan 2026 10:20:45 -0800
parents 46daba6e3cf4
children
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46daba6e3cf4 Few python scrtips to show how to use asychio.
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1 # # Bank Account
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2 #
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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.
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4 #
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5 # Task
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6 #
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7 # Identify the concurrency bugs in the implementation.
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8 #
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9 # Explain why these bugs occur.
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10 #
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11 # Fix the implementation without modifying the existing BankAccount class directly.
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12 #
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13 # You may use subclassing (Python) or embedding (Go-style composition), depending on the language you choose.
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14 #
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15 # Ensure your solution is thread-safe and produces the correct final balance (1200).
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16
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17 from threading import Lock
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18 from concurrent.futures import ThreadPoolExecutor
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19 import time
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20
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21 class BankAccount:
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22 def __init__(self, balance):
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23 self.balance = balance
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24 self._lock = Lock()
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25
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26 def deposit(self, amount):
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27 while (self._lock.locked()):
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28 pass
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29 self._lock.acquire()
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30 new_balance = self.balance + amount # read
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31 time.sleep(0.1) # simulate delay
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32 self.balance = new_balance # write
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33 self._lock.release()
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36 account = BankAccount(0)
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37
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38 with ThreadPoolExecutor(max_workers=2) as executor:
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39 futures = [
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40 executor.submit(account.deposit, 500),
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41 executor.submit(account.deposit, 700),
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42 ]
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43 print(account.balance)