Python 3.1.2
我在multiprocessing.Process产生的两个线程之间共享变量时遇到问题。这是一个简单的布尔变量，它应该确定线程是否应该运行或应该停止执行。下面是在三种情况下显示的简化代码（但使用与我的原始代码相同的机制）：
- threading.Thread 类型和 self.is_running bool 类型的主类beeing [工作正常]。
- multiprocess.Process 类型和 self.is_running bool 类型的主类beeing [不工作。子线程拥有 self.is_running 的本地副本，而不是共享它]。
- multiprocess.Process 类型和 self.is_running 的主类beeing 是 multiprocessing.Value("b", True) [工作正常] 类型。
我想了解为什么它以这种方式而不是另一种方式工作。（即为什么第 2 点没有像我假设的那样工作）。
测试是从 python 的解释器完成的：
from testclass import *
d = TestClass()
d.start()
d.stop()
以下是第 1 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 2 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()