関数では、2 秒ごとに 1 行を呼び出したいと考えています。スリープ機能を使用するたびに、コードは2秒間待機してから次の命令に進みます。しかし、他の命令を邪魔することなく、2秒ごとに関数を呼び出したいです。例;
a = None
def foo():
bar()
a = a * 12
print "A : ",a
def bar():
a = 0
2 秒ごとに a をリセットする必要があります。ただし、2 秒で a の値がインクリメントされて表示されるはずです。出来ますか ？どのように ？
スレッドとロックを使用して、お客様のニーズにアプローチします。
実際、友人の Pepe が作成したオープンソースの ThreadPool が大好きです。
これが ThreadPool コードであり、その後、考えられる解決策は次のとおりです。
#! /usr/bin/python
# -*- coding: utf-8 -*-
# File: threadPool.py
import threading
import Queue
import time
import sys
import traceback
import datetime
Instance = None
def getInstance():
global Instance
if not Instance:
Instance = ThreadPool()
return Instance
class ThreadPool:
def __init__(self,maxWorkers = 10):
self.tasks = Queue.Queue()
self.workers = 0
self.working = 0
self.maxWorkers = maxWorkers
self.allKilled = threading.Event()
self.countLock = threading.RLock()
self.timers = {}
self.timersLock = threading.Lock()
self.timersThreadLock = threading.Lock()
self.timersEvent = threading.Event()
self.allKilled.set()
def run(self,target,callback = None, *args, **kargs):
""" starts task.
target = callable to run with *args and **kargs arguments.
callback = callable executed when target ends
callback sould accept one parameter where target's
return value is passed.
If callback is None it's ignored.
"""
self.countLock.acquire()
if not self.workers:
self.addWorker()
self.countLock.release()
self.tasks.put((target,callback,args,kargs))
def setMaxWorkers(self,num):
""" Sets the maximum workers to create.
num = max workers
If number passed is lower than active workers
it will kill workers to match that number.
"""
self.countLock.acquire()
self.maxWorkers = num
if self.workers > self.maxWorkers:
self.killWorker(self.workers - self.maxWorkers)
self.countLock.release()
def addWorker(self,num = 1):
""" Add workers.
num = number of workers to create/add.
"""
for x in xrange(num):
self.countLock.acquire()
self.workers += 1
self.allKilled.clear()
self.countLock.release()
t = threading.Thread(target = self.__workerThread)
t.setDaemon(True)
t.start()
def killWorker(self,num = 1):
""" Kill workers.
num = number of workers to kill.
"""
self.countLock.acquire()
if num > self.workers:
num = self.workers
self.countLock.release()
for x in xrange(num):
self.tasks.put("exit")
def killAllWorkers(self,wait = None):
""" Kill all active workers.
wait = seconds to wait until last worker ends
if None it waits forever.
"""
self.countLock.acquire()
self.killWorker(self.workers)
self.countLock.release()
self.allKilled.wait(wait)
def __workerThread(self):
while True:
task = self.tasks.get()
# exit is "special" tasks to kill thread
if task == "exit":
break
self.countLock.acquire()
self.working += 1
if (self.working >= self.workers) and (self.workers < self.maxWorkers): # create thread on demand
self.addWorker()
self.countLock.release()
fun,cb,args,kargs = task
try:
ret = fun(*args,**kargs)
if cb:
cb(ret)
except:
ty,val,tb = sys.exc_info()
print "Thread Catch:%s" % "".join(traceback.format_exception(ty,val,tb))
self.countLock.acquire()
self.working -= 1
self.countLock.release()
del(fun) # Dereference all
del(cb)
del(args)
del(kargs)
del(task)
self.countLock.acquire()
self.workers -= 1
if not self.workers:
self.allKilled.set()
self.countLock.release()
def timer(self, cb, period):
""" Add or remove timers.
cb = callback function.
period = period in seconds (float)
if period is 0 timer is deleted.
"""
self.run(self.__timerThread, None, cb, period)
def __timerThread(self, cb, period):
self.timersLock.acquire()
self.timersEvent.set()
if not period:
if cb in self.timers:
del(self.timers[cb])
self.timersLock.release()
return
self.timers[cb] = [period,time.time()]
self.timersLock.release()
if not self.timersThreadLock.acquire(0):
return
while True:
self.timersLock.acquire()
if len(self.timers) == 0:
self.timersThreadLock.release()
self.timersLock.release()
break
minWait = 30*24*3600
now = time.time()
for k,v in self.timers.items():
period, last = v
wait = period - (now - last)
if wait <=0:
self.run(k)
wait = period
v[1] = now
if wait < minWait:
minWait = wait
self.timersLock.release()
self.timersEvent.wait(minWait)
self.timersEvent.clear()
そして可能な解決策：
#! /usr/bin/python
# -*- coding: utf-8 -*-
# File: a.py
import threadPool
import time
import threading
class A:
def __init__(self):
self.a = 1
self.alock = threading.Lock()
self.tp = threadPool.getInstance()
def bar(self):
self.alock.acquire()
self.a = 1
self.alock.release()
def foo(self):
self.tp.timer(self.bar, 2)
while True:
self.alock.acquire()
self.a = self.a * 12
self.alock.release()
print "A : ",self.a
time.sleep(0.1)
a = A()
a.foo()
走る：
$ python a.py