Comments (3)
python3.10中的新变化:
https://stackoverflow.com/questions/69993959/python-threads-difference-for-3-10-and-others
demo:
from threading import Thread
i = 0
def foo():
global i
for _ in range(1000000):
i += 1
def bar():
global i
for _ in range(1000000):
i -= 1
threads = []
for _ in range(10):
thread = Thread(target=foo)
threads.append(thread)
for _ in range(10):
thread = Thread(target=bar)
threads.append(thread)
for thread in threads:
thread.start()
for thread in threads:
thread.join()
print(i)
assert i == 0
我是认为,这从侧面说明“Python还不是一个很稳定的语言”,像这种特性,无论是否是原子的,早就应该固定下来,不发生变化。
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你好,value 是局部或是全部不是重点,重点在于 "+=" 运算符不是原子。在它的执行过程中有可能会被插入其他语句,所以不是线程安全的。
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python3.10中的新变化: https://stackoverflow.com/questions/69993959/python-threads-difference-for-3-10-and-others
demo:
from threading import Thread i = 0 def foo(): global i for _ in range(1000000): i += 1 def bar(): global i for _ in range(1000000): i -= 1 threads = [] for _ in range(10): thread = Thread(target=foo) threads.append(thread) for _ in range(10): thread = Thread(target=bar) threads.append(thread) for thread in threads: thread.start() for thread in threads: thread.join() print(i) assert i == 0我是认为,这从侧面说明“Python还不是一个很稳定的语言”,像这种特性,无论是否是原子的,早就应该固定下来,不发生变化。
很有意思,3.10 的这个改动我也是第一次看到。这小部分内容我没有写进图书版里,如果之后修订,我考虑调整下措辞或示例来加强说服力。大观点会维持不变:不依赖任何直觉看上去像(未文档化的)“原子操作”的行为实现并发安全。
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