thread 多线程

一、为什么重写mythread类里写了run()在main里没有调用，而调用了没有写的start()

start()让run()在新线程里面运行。你直接调用run()就是在当前线程运行了。 

start()调用_thread的start_new_thread去运行一个bootstrap方法，在里面做一些准备工作后会调用run() 

1.简单的多线程

from time import sleep, ctime
import threading
def fab(x):
    sleep(5)
    print 'fab', ctime()
    if x < 3:        
        return 1
    return (fab(x-1)+fab(x-2))
    
def sumx(x):
    sleep(5)
    print 'sumx', ctime()
    if x < 2:
        return 1
    return (x+sumx(x-1))
def mulx(x):
    sleep(5)
    print 'mulx', ctime()
    if x < 2:
        return 1
    return (x*mulx(x-1))
def main():
    a = threading.Thread(target=fab, args=(1,))
    sleep(1)
    b = threading.Thread(target=sumx, args=(1,))
    sleep(1)
    c = threading.Thread(target=mulx, args=(1,))
    a.start()
    b.start()
    c.start()
    print threading.activeCount()
    print threading.enumerate()
    a.join()
    b.join()
    c.join()
if __name__ == '__main__':
    main()

二、复杂的多线程

import threading
from time import sleep, ctime
loops = [4, 2]
class MyThread(threading.Thread):
     
    def __init__(self, func, args, name=''):
      threading.Thread.__init__(self)
      self.name = name
      self.func = func
      self.args = args
   
    def getResult(self):
        return self.res
     
    def run(self):
        print 'starting', self.name, 'at:', ctime()
        self.res = apply(self.func, self.args)
        print self.name, 'finished at:', ctime()
         
def fib(x):
    sleep(0.005)
    if x < 2: return 1
    return (fib(x-2) + fib(x-1))
def fac(x):
    sleep(0.1)
    if x <2: return 1
    return (x * fac(x-1))   
   
def sum(x):
    sleep(0.1)
    if x <2: return 1
    return (x + sum(x-1))
   
funcs = [fib, fac, sum]
n = 12
   
def main():
    nfuncs = range(len(funcs))
   
   
    print '*** SINGLE THREAD'
    for i in nfuncs:
        print 'starting', funcs[i].__name__, 'at:', ctime()
        print funcs[i](n)
        print funcs[i].__name__, 'finished at:', ctime()
       
    print '\n*** MULTIPLE THREADS'
    threads = []
    for i in nfuncs:
        t = MyThread(funcs[i], (n,), funcs[i].__name__)
        threads.append(t)
   
    for i in nfuncs:
        threads[i].start()
   
    for i in nfuncs:
        threads[i].join()
        print threads[i].getResult()
       
    print 'all DONE'
   
      
if __name__ == '__main__':
    main()

三.多线程实例同时下载网页,args传入参数为元组

import urllib
import threading
url = ['http://www.baidu.com', 'http://pan.baidu.com', 'http://tieba.baidu.com']
def openurl(url, x):
    urllib.urlretrieve(url, 'd:\\'+str(x)+'.txt')
def main():
    print 'start...........'
    list1 = []
    loops = range(len(url))
    for i in loops:
        t = threading.Thread(target=openurl, args=(url[i],i))
        list1.append(t)
    for i in loops:
        list1[i].start()
    for i in loops:
        list1[i].join()  
    print 'all down'
if __name__ == '__main__':
    main()

四、实例化类继承类初始化，重写run()函数

import urllib
import threading
url = ['http://www.baidu.com', 'http://pan.baidu.com', 'http://tieba.baidu.com']
class downloader(threading.Thread):
    def __init__(self, url, x):
        threading.Thread.__init__(self)
        self.url = url
        self.x = x
       
    def run(self):
        urllib.urlretrieve(self.url, 'd:\\'+str(self.x)+'.txt')
for i in range(len(url)):
    i = downloader(url[i], i)
    i.start()

来自为知笔记(Wiz)