Python(2.7.x)多線程的簡單示例

Python線程的使用有兩種：基於thread模塊的start_new_thread方法和基於threading模塊的Thread類。

1. 基於thread模塊的start_new_thread方法：

import thread
from time import sleep 
from random import randint

def display(name, count):
	if count > 1:
		print "Now, %s has %d apples.\n" % (name, count),
	elif count == 1:
		print "Now, %s has only one apple.\n" % name,
	else:
		print "Now, %s has not any apples.\n" % name,
                
def eat_apple(name, count):
	display(name, count)
	while count > 0:
		print "%s eats an apple.\n" % name,
		count -= 1
		display(name, count)
		sleep(randint(1, 3))

try:
	thread.start_new_thread(eat_apple, ("Huey", 3) )
	thread.start_new_thread(eat_apple, ("Sugar", 5) )
except Exception, e:
	print "Thread Error\n",

基於thread模塊的start_new_thread方法已經不推薦使用了，在IDLE中這段代碼可以正確運行，在其他環境下可能會報如下錯誤：

Unhandled exception in thread started by
sys.excepthook is missing
lost sys.stderr

原因：啓動線程之後，須確保主線程等待所有子線程返回結果後再退出，如果主線程比子線程早結束，無論其子線程是否是後臺線程，都將會中斷，拋出這個異常 。

2. 基於threading模塊的Thread類：

from threading import Thread
from time import sleep
from random import randint

def display(name, count):
	if count > 1:
		print "Now, %s has %d apples.\n" % (name, count),
	elif count == 1:
		print "Now, %s has only an apple.\n" % name,
	else:
		print "Now, %s has not any apples.\n" % name,
                
def eat_apple(name, count):
	display(name, count)
	while count > 0:
		print "%s eats an apple.\n" % name,
		count -= 1
		display(name, count)
		sleep(randint(1, 3))

class MyThread(Thread):
	"""docstring for MyThread"""
	def __init__(self, name, count):
		super(MyThread, self).__init__()
		self.name = name
		self.count = count
	def run(self):
		eat_apple(self.name, self.count)

huey = MyThread("Huey", 3)
sugar = MyThread("Sugar", 5)

huey.start()
sugar.start()

3. 線程同步問題：

# encoding: utf-8

from threading import Thread
from threading import Lock
from time import sleep
from random import randint

# 倉庫有十個槽位
storehouse = [0] * 10
# 線程鎖
lock = Lock()

class Producer(Thread):
	u"""生產者，依次往倉庫裏的十個槽位生產產品"""
	def __init__(self):
		super(Producer, self).__init__()	
	def run(self):
		print "Producer starts producing...\n",
		x = 0
		while x < len(storehouse):
			# 獲取鎖
			lock.acquire()
			print "Producer is producing the No.%d product.\n" % x, 
			storehouse[x] = 1
			print "Now, the storehouse is %s\n" % storehouse,
			# 釋放鎖
			lock.release()
			x += 1
			sleep(randint(1, 3))
		print "Producer has produced all the products!\n",

class Consumer(Thread):
	u"""消費者，依次消費倉庫裏十個槽位的產品，如果槽位還沒有商品，則等待生產者生產"""
	def __init__(self):
		super(Consumer, self).__init__()	
	def run(self):
		print "Consumer starts consuming...\n",
		x = 0
		while x < len(storehouse):
			print "Consumer wants to consume a product...\n",
			# 獲取鎖
			lock.acquire()
			if storehouse[x] <= 0:
				print "There are not any products, the consumer waits.\n",
			else:
				print "Consumer is consuming the No.%d product.\n" % x,
				storehouse[x] = -1
				print "Now, the storehouse is %s\n" % storehouse,
				x += 1
			# 釋放鎖
			lock.release()
			sleep(randint(1, 3))
		print "Consumer has consumed all the products!\n",


print "Originally, the storehouse is ", storehouse

producer = Producer()
consumer = Consumer()
producer.start()
consumer.start()

# 阻塞線程，等待其他線程結束
producer.join()
consumer.join()

print "Finally, the storehouse is ", storehouse