Python 的线程
Python的参数传递其实传递的是对象，当传递可变对象(列表、队列)时相当于引用传递，可以修改对象的原始值，当传递不可变对象(字符串、整型)时就相当于传值，不能直接修改原始对象。
0x00 单线程
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from time import time,ctime,sleep
def music(arg):
for x in range(2):
print "I'm listening to %s. %s" % (arg,ctime())
sleep(1)
def movie(arg):
for x in range(2):
print "I'm watching %s. %s" % (arg,ctime())
sleep(5)
if __name__ == '__main__':
start = int(time())
music(u'我')
movie(u'可是')
print "All over time:%s" % ctime()
print "Used time:%d" % int(time()-start)
0x01 多线程
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import re
import requests
import threading
from time import time,ctime,sleep
INDEX = 0
def http_get(sites):
global INDEX
while INDEX < len(sites):
url = sites[INDEX]
INDEX += 1
resp = requests.get(url, timeout=3)
resp.encoding = resp.apparent_encoding
title = re.search(r'<title>(.*?)</title>', resp.text).group(1)
print "URL:%-30sTitle:%s" % (url, title)
sites = [
"http://www.baidu.com",
"http://www.qq.com",
"http://www.github.com",
"http://www.jingyingba.com",
]
if __name__ == '__main__':
start = int(time())
threads = []
for i in range(0, 3):
t = threading.Thread(target=http_get, args=(sites,))
threads.append(t)
for t in threads:
#t.setDaemon(True) #设为守护线程,主线程结束后不管子线程是否完成,立即结束
t.start()
for t in threads:
t.join() #主线程阻塞，等待子线程完成
print "Used time:%d" % int(time() - start)
0x02 线程同步
使用多线程时若线程共用一个资源则可能导致线程竞争问题，可以通过互斥锁和队列来解决
- 线程竞争
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import re
import requests
import threading
from time import time,ctime,sleep
num = 0
def test():
global num
sleep(1)
num = num+1
msg = 'Number: ' + str(num)
print msg
if __name__ == '__main__':
start = int(time())
threads = []
for i in range(0, 20):
t = threading.Thread(target=test)
threads.append(t)
for t in threads:
t.setDaemon(True)
t.start()
for t in threads:
t.join()
print "Used time:%d" % int(time() - start)
- 互斥锁
#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
使用步骤：
1. 创建互斥锁 mutex = threading.Lock()
2. 锁定 mutex.acquire([timeout])
3. 释放 mutex.release()
"""
import re
import requests
import threading
from time import time,ctime,sleep
num = 0
mutex = threading.Lock()
def test():
global num
sleep(0.5)
mutex.acquire() #这里存在线程竞争，设置互斥锁
num = num+1
mutex.release()
msg = 'set num to '+str(num)
mutex.acquire() #输出有可能错乱，还是线程竞争问题
print msg
mutex.release()
if __name__ == '__main__':
start = int(time())
threads = []
for i in range(0, 20):
t = threading.Thread(target=test)
threads.append(t)
for t in threads:
t.setDaemon(True)
t.start()
for t in threads:
t.join()
print "Total use time %d" % int(time() - start)
- 队列(推荐)
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import re
import random
import Queue
import requests
import threading
from time import time,ctime,sleep
queue = Queue.Queue()
for i in xrange(1,20+1):
queue.put(i) #put一次队列里的任务数就加1
def test(queue):
while not queue.empty():
sleep(random.random()) #随机生成的一个实数，它在(0,1)范围内
i = queue.get()
print i
queue.task_done()
if __name__ == '__main__':
start = int(time())
threads = []
for x in range(0, 20):
t = threading.Thread(target=test, args=(queue,))
threads.append(t)
for t in threads:
t.setDaemon(True)
t.start()
queue.join() #等待队列里的任务数为0，即队列为空任务完成
print "Total use time %d" % int(time() - start)
0x03 多线程与类与队列
#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
使用步骤：
1. 继承线程类 threading.Thread
2. 重写线程类的__init__方法
3. 重写线程类的run方法
4. 继承类每实例化一次就创建一个线程
__init__方法一般接收外部参数并存放到实例变量
实例化对象调用start()方法后运行了run()方法
"""
import re
import random
import Queue
import requests
import threading
from time import time,ctime,sleep
hosts = [
"http://www.baidu.com",
"http://www.qq.com",
"http://www.github.com",
"http://www.jingyingba.com"
]
queue = Queue.Queue()
class ThreadTest(threading.Thread):
"docstring for ThreadTest"
def __init__(self, queue):
threading.Thread.__init__(self)
self.queue = queue
def run(self):
while not self.queue.empty():
host = self.queue.get()
resp = requests.get(host)
resp.encoding = resp.apparent_encoding
title = re.search(r'<title>(.*?)</title>',resp.text,re.I).group(1)
print "URL:%-30sTitle:%s" % (host, title)
self.queue.task_done()
def main():
for host in hosts:
queue.put(host)
for x in xrange(1,4):
t = ThreadTest(queue)
t.setDaemon(True)
t.start()
queue.join()
if __name__ == '__main__':
start = time()
main()
print "Total use time %d" % int(time() - start)
