【脚本语言系列】关于Python多线程编程Threading, 你需要知道的事

如何使用Threading

Python中的Thread,Threading模块可用于多线程。Threading模块是Thread的封装。
一般而言，使用Threading模块即可。

# -*- coding: utf-8 -*-
#
import thread
def run(n):
    for i in range(n):
        print i
print thread.start_new_thread(run,(4,))
print thread.start_new_thread(run,(2,))
print thread.start_new_thread(run,(),{'n':4})

# -*- coding: utf-8 -*-
#
import threading
class mythread(threading.Thread):
    def __init__(self, num):
        threading.Thread.__init__(self)
        self.num = num
    def run(self):
        print 'I am ', self.num
t1 = mythread(1)
t2 = mythread(2)
t3 = mythread(3)
print t1.start()
print t2.start()
print t3.start()

# -*- coding: utf-8 -*-
#
import threading
def run(x, y):
    for i in range(x, y):
        print i
t1 = threading.Thread(target=run, args=(15, 20))
t1.start()
t2 = threading.Thread(target=run, args=(7, 11))
t2.start()

# -*- coding: utf-8 -*-
#
import threading
import time
class Mythread(threading.Thread):
    def __init__(self, id):
        threading.Thread.__init__(self)
        self.id = id
    def run(self):
        x = 0
        time.sleep(5)
        print self.id
def func():
    t.start()
    t.join()
    for i in range(5):
        print i
t = Mythread(2)
func()

# -*- coding: utf-8 -*-
#
import threading
import time
class Mythread(threading.Thread):
    def __init__(self, threadname):
        threading.Thread.__init__(self, name=threadname)
    def run(self):
        time.sleep(5)
        print self.getName()
def func1():
    t1.start()
    print "func1 done"
def func2():
    t2.start()
    print "func2 done"
t1 = Mythread("t1")
t2 = Mythread("t2")
t2.setDaemon(True)
func1()
func2()

线程同步

为了保证多个线程共同对某个数据进行修改造成的不可预料的后果，需要对多个线程进行同步。使用Thread对象的Lock和RLock可以实现简单的线程同步。

# -*- coding: utf-8 -*-
#
import threading
import time
class mythread(threading.Thread):
    def __init__(self, threadname):
        threading.Thread.__init__(self, name = threadname)
    def run(self):
        global x
        lock.acquire()
        for i in range(3):
            x = x+1
        time.sleep(2)
        print x
        lock.release()
lock = threading.RLock()
t1 = []
for i in range(10):
    t = mythread(str(i))
    t1.append(t)
x=0
for i in t1:
    i.start()

# -*- coding: utf-8 -*-
#
import threading
class Producer(threading.Thread):
    def __init__(self, threadname):
        threading.Thread.__init__(self, name=threadname)
    def run(self):
        global x
        con.acquire()
        if x == 1000000:
            con.wait()
            pass
        else:
            for i in range(1000000):
                x = x + 1
            con.notify()
        print x
        con.release()
class Consumer(threading.Thread):
    def __init__(self, threadname):
        threading.Thread.__init__(self, name=threadname)
    def run(self):
        global x
        con.acquire()
        if x == 0:
            con.wait()
            pass
        else:
            for i in range(1000000):
                x = x - 1
            con.notify()
        print x
        con.release()        
con = threading.Condition()
x=0
p = Producer('Producer')
c = Consumer('Consumer')
p.start()
c.start()
p.join()
c.join()
print x

线程间通讯

Python提供了Event对象用于线程间的相互通讯。Event对象是由线程设置的信号标志，如果信号标志为真，则其他线程等待直到信号解除。Event对象包含了设置信号、清楚信号、等待等用于实现线程间的通讯。

# -*- coding: utf-8 -*-
#
import threading
class mythread(threading.Thread):
    def __init__(self, threadname):
        threading.Thread.__init__(self, name = threadname)
    def run(self):
        global event
        if event.isSet():
            event.clear()
            event.wait()
            print self.getName()
        else:
            print self.getName()
            event.set()
event = threading.Event()
event.set()
t1 = []
for i in range(10):
    t = mythread(str(i))
    t1.append(t)
for i in t1:
    i.start()

什么是Threading

进程是操作系统中应用程序的执行实例，而线程是进程内部的一个执行单元。
当系统创建一个进程后，也就创建了一个主线程。
每个进程至少有一个线程，也可以有多个线程。
在程序中使用多线程可以实现并行处理，充分利用CPU。
Python提供了对多线程的支持。在Python中可以方便地使用多线程编程。