✨ 并发编程处理

Day61-65/63.Python中的并发编程-1.md

@@ -374,6 +374,63 @@ if __name__ == '__main__':
 
 > **思考**：将上面的代码修改为5个线程向银行账户存钱，5个线程从银行账户取钱，取钱的线程在银行账户余额不足时，需要停下来等待存钱的线程将钱存入后再尝试取钱。这里需要用到线程调度的知识，大家可以自行研究下`threading`模块中的`Condition`类，看看是否能够完成这个任务。
 
+解答：
+```python
+import time
+from concurrent.futures import ThreadPoolExecutor
+from threading import Condition
+
+class Account(object):
+    """银行账户"""
+
+    def __init__(self):
+        self.balance = 0.0
+        # 初始化一个Condition对象，用于线程间协调
+        self.condition = Condition()
+
+    def deposit(self, money):
+        # 存钱操作
+        with self.condition:
+            # 更新余额
+            new_balance = self.balance + money
+            time.sleep(0.01)  # 模拟延迟
+            self.balance = new_balance
+            # 通知所有等待的线程，存钱操作完成
+            self.condition.notify_all()
+            print(f'Deposited {money}, new balance is {self.balance}')
+
+    def withdraw(self, money):
+        # 取钱操作
+        with self.condition:
+            # 如果余额不足，等待
+            while self.balance < money:
+                self.condition.wait()  # 等待通知
+            # 更新余额
+            new_balance = self.balance - money
+            time.sleep(0.01)  # 模拟延迟
+            self.balance = new_balance
+            print(f'Withdrew {money}, new balance is {self.balance}')
+
+
+def main():
+    """主函数"""
+    account = Account()
+    # 使用ThreadPoolExecutor创建一个线程池
+    with ThreadPoolExecutor(max_workers=10) as pool:
+        # 提交5个存钱任务和5个取钱任务
+        for _ in range(5):
+            pool.submit(account.deposit, 1)
+            pool.submit(account.withdraw, 1)
+    # 等待所有线程完成
+    time.sleep(2)
+    print(f'Final balance: {account.balance}')
+
+
+if __name__ == '__main__':
+    main()
+
+```
+
 ### GIL问题
 
 如果使用官方的 Python 解释器（通常称之为 CPython）运行 Python 程序，我们并不能通过使用多线程的方式将 CPU 的利用率提升到逼近400%（对于4核 CPU）或逼近800%（对于8核 CPU）这样的水平，因为 CPython 在执行代码时，会受到 GIL（全局解释器锁）的限制。具体的说，CPython 在执行任何代码时，都需要对应的线程先获得 GIL，然后每执行100条（字节码）指令，CPython 就会让获得 GIL 的线程主动释放 GIL，这样别的线程才有机会执行。因为 GIL 的存在，无论你的 CPU 有多少个核，我们编写的 Python 代码也没有机会真正并行的执行。

Day61-65/allocation.py

@@ -0,0 +1,42 @@
+import time
+from concurrent.futures import ThreadPoolExecutor
+from threading import Condition, Thread
+
+class Account(object):
+    """银行账户"""
+
+    def __init__(self):
+        self.balance = 0.0
+        self.condition = Condition()
+
+    def deposit(self, money):
+        with self.condition:
+            new_balance = self.balance + money
+            time.sleep(0.01)
+            self.balance = new_balance
+            self.condition.notify_all()  # 通知所有等待的线程
+            print(f'Deposited {money}, new balance is {self.balance}')
+
+    def withdraw(self, money):
+        with self.condition:
+            while self.balance < money:
+                self.condition.wait()  # 等待通知
+            new_balance = self.balance - money
+            time.sleep(0.01)
+            self.balance = new_balance
+            print(f'Withdrew {money}, new balance is {self.balance}')
+
+
+def main():
+    """主函数"""
+    account = Account()
+    with ThreadPoolExecutor(max_workers=10) as pool:
+        for _ in range(5):
+            pool.submit(account.deposit, 1)
+            pool.submit(account.withdraw, 1)
+    time.sleep(2)  # 等待所有线程完成
+    print(f'Final balance: {account.balance}')
+
+
+if __name__ == '__main__':
+    main()

Day61-65/formal.py

@@ -0,0 +1,32 @@
+import time
+
+from concurrent.futures import ThreadPoolExecutor
+from threading import RLock
+
+
+class Account(object):
+    """银行账户"""
+
+    def __init__(self):
+        self.balance = 0.0
+        self.lock = RLock()
+
+    def deposit(self, money):
+        # 通过上下文语法获得锁和释放锁
+        with self.lock:
+            new_balance = self.balance + money
+            time.sleep(0.01)
+            self.balance = new_balance
+
+
+def main():
+    """主函数"""
+    account = Account()
+    with ThreadPoolExecutor(max_workers=16) as pool:
+        for _ in range(100):
+            pool.submit(account.deposit, 1)
+    print(account.balance)
+
+
+if __name__ == '__main__':
+    main()