多线程案例python3.8和3.10运行结果不一致
import threadingtotal = 0
def add():
global total
for i in range(10000000):
total += 1
def desc():
global total
for i in range(10000000):
total -= 1
thread1 = threading.Thread(target=add)
thread2 = threading.Thread(target=desc)
thread1.start()
thread2.start()
thread1.join()
thread2.join()
print(total)
Python3高级核心技术97讲课程中，多线程的一个案例，在python3.8版本中，total最终结果是随机的，不为0，但是换成python3.10或者3.11版本，结果总是为0，非常奇怪，求大佬解答。 因为执行速度不一样，子线程都没执行完就输出结果了，你这线程写的很有问题 3.10 修复另一个bug导致的看起来线程安全了实际还是不安全的 应该是 3.10 以下的 BUG，理论上 3.10、3,11的结果才是对的，给代码上锁以后，使用 3.8 执行，结果也是 0
import threading
total = 0
lock = threading.Lock()
def add():
global total
for i in range(10000000):
lock.acquire()
total += 1
lock.release()
def desc():
global total
for i in range(10000000):
lock.acquire()
total -= 1
lock.release()
thread1 = threading.Thread(target=add)
thread2 = threading.Thread(target=desc)
thread1.start()
thread2.start()
thread1.join()
thread2.join()
print(total)
import threading
total = 0
def add():
global total
for i in range(10000000):
total += 1
def desc():
global total
for i in range(10000000):
total -= 1
threads = []
t1 = threading.Thread(target=add)
t2 = threading.Thread(target=desc)
threads.append(t1)
threads.append(t2)
for t in threads:
t.start()
t.join()
print(total) import threading
total = 0
def add():
global total
for i in range(10000000):
total += 1
def desc():
global total
for i in range(10000000):
total -= 1
# threads = []
# t1 = threading.Thread(target=add)
# t2 = threading.Thread(target=desc)
# threads.append(t1)
# threads.append(t2)
# for t in threads:
# t.start()
# t.join()
thread1 = threading.Thread(target=add)
thread2 = threading.Thread(target=desc)
thread1.start()
# thread2.start()
thread1.join()
thread2.start()
thread2.join()
# time.sleep(10)
print(total) 线程不能共享全局变量了，像不安全的。
黑色小白 发表于 2022-12-6 23:16
3.10 修复另一个bug导致的看起来线程安全了实际还是不安全的
请教大佬，3.10以上版本具体修复了什么bug，导致这种情况看起来是线程安全的？ wangwh27 发表于 2022-12-7 14:38
请教大佬，3.10以上版本具体修复了什么bug，导致这种情况看起来是线程安全的？
https://github.com/python/cpython/commit/4958f5d69dd2bf86866c43491caf72f774ddec97
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