Python 3.1.2
我在使用 multiprocessing.Process 创建的两个线程之间共享变量时遇到了问题。这是一个简单的布尔变量，应该确定线程是否应该运行或停止执行。下面是三种情况下的简化代码（但使用与我的原始代码相同的机制）：
- 主类为
threading.Thread类型，self.is_running是bool类型 [正常工作]。 - 主类为
multiprocess.Process类型，self.is_running是bool类型 [不起作用。子线程有自己的self.is_running的本地副本而不是共享它]。 - 主类为
multiprocess.Process类型，self.is_running是multiprocessing.Value("b", True)类型 [正常工作]。
我想知道为什么会这样，而不是另一种方式。（即为什么第二种情况没有按照我的假设工作）。
测试是在 Python 解释器中进行的：
from testclass import *
d = TestClass()
d.start()
d.stop()
以下是第一点的示例：
import threading
import time
import queue
import multiprocessing
class TestClass(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
self.q = queue.Queue(10)
self.is_running = True
self.sema = threading.Semaphore()
def isRunning(self):
self.sema.acquire()
print ("Am I running?", self.is_running)
z = self.is_running
self.sema.release()
return z
def stop(self):
self.sema.acquire()
self.is_running = False
print("STOPPING")
self.sema.release()
def reader(self):
while self.isRunning():
print("R] Reading!")
try:
data = self.q.get(timeout=1)
except:
print("R] NO DATA!")
else:
print("R] Read: ", data)
def writer(self):
while self.isRunning():
print("W] Writing!")
self.q.put(time.time())
time.sleep(2)
def run(self):
tr = threading.Thread(target=self.reader)
tw = threading.Thread(target=self.writer)
tr.start()
tw.start()
tr.join()
tw.join()
第二点的示例：
import threading
import time
import queue
import multiprocessing
class Test(multiprocessing.Process):
def __init__(self):
multiprocessing.Process.__init__(self)
self.q = queue.Queue(10)
self.is_running = True
self.sema = threading.Semaphore()
def isRunning(self):
self.sema.acquire()
print ("Am I running?", self.is_running)
z = self.is_running
self.sema.release()
return z
def stop(self):
self.sema.acquire()
self.is_running = False
print("STOPPING")
self.sema.release()
def reader(self):
while self.isRunning():
print("R] Reading!")
try:
data = self.q.get(timeout=1)
except:
print("R] NO DATA!")
else:
print("R] Read: ", data)
def writer(self):
while self.isRunning():
print("W] Writing!")
self.q.put(time.time())
time.sleep(2)
def run(self):
tr = threading.Thread(target=self.reader)
tw = threading.Thread(target=self.writer)
tr.start()
tw.start()
tr.join()
tw.join()
第3点的示例:
import threading
import time
import queue
import multiprocessing
class TestClass(multiprocessing.Process):
def __init__(self):
multiprocessing.Process.__init__(self)
self.q = queue.Queue(10)
self.is_running = multiprocessing.Value("b", True)
self.sema = threading.Semaphore()
def isRunning(self):
self.sema.acquire()
print ("Am I running?", self.is_running)
z = self.is_running.value
self.sema.release()
return z
def stop(self):
self.sema.acquire()
self.is_running.value = False
print("STOPPING")
self.sema.release()
def reader(self):
while self.isRunning():
print("R] Reading!")
try:
data = self.q.get(timeout=1)
except:
print("R] NO DATA!")
else:
print("R] Read: ", data)
def writer(self):
while self.isRunning():
print("W] Writing!")
self.q.put(time.time())
time.sleep(2)
def run(self):
tr = threading.Thread(target=self.reader)
tw = threading.Thread(target=self.writer)
tr.start()
tw.start()
tr.join()
tw.join()