Python Threading

threading总结：http://www.cnblogs.com/tkqasn/p/5700281.html

Threading模块下的thread类的使用:

函数	描述
run()	通常需要重写，编写代码实现 做需要的功能。定义线程功能的函数
getName()	获得线程对象名称
setName()	设置线程对象名称
start()	启动线程
join(timeout)	在一个线程B中调用threada.join()，则threada结束后，线程B才会接着threada.join()往后运行，timeout可以设置等待时间。
setDaemon()	主线程A启动了子线程B，调用b.setDaemaon(True)，则主线程结束时，会把子线程B也杀死，必须在start()之前调用。默认为False。
isDaemon()	判断线程是否随主线程一起结束。
isAlive()	检查线程是否在运行中。
Lock()	分配一个LockType类型的锁对象
Rlock()	递归锁，支持多把锁
acquire()	加锁，锁住相应的资源
release()	释放锁,释放相应的资源

 

锁：lock，RLock，BoundedSemaphore

1. 普通锁 threading.Lock() 只能解一把锁，有多把锁就会出不来，把自己锁死

import threading
import time

lock = threading.Lock()

def download(url):
    lock.acquire()
    time.sleep(1)
    print(url)
    lock.release()

urls = [123, 234, 456, 567, 678]
for i in urls:
    t = threading.Thread(target=download, args=[i])
    t.start()

print("end")

2. 递归锁 threading.Rlock()  可以解多把锁

import threading
import time

lock = threading.RLock()

def download(url):
    lock.acquire()
    lock.acquire()
    time.sleep(1)
    print(url)
    lock.release()
    lock.release()

urls = [123, 234, 456, 567, 678]
for i in urls:
    t = threading.Thread(target=download, args=[i])
    t.start()

print("end")

3.信号量：threading.BoundedSemaphore

举例：厕所外面加锁，一个厕所有2个坑。 这就是所谓的信号量

import threading
import time

lock = threading.BoundedSemaphore(2)

def download(url):
    lock.acquire()
    time.sleep(1)
    print(url)
    lock.release()

urls = [123, 234, 456, 567, 678]
for i in urls:
    t = threading.Thread(target=download, args=[i])
    t.start()

print("end")

 

Condition, Event

1.Event全部锁住等待释放

python线程的Event用于主线程控制其他线程的执行，事件主要提供了三个方法 set、wait、clear。

事件处理的机制：全局定义了一个“Flag”，如果“Flag”值为 False，那么当程序执行 event.wait 方法时就会阻塞，如果“Flag”值为True，那么event.wait 方法时便不再阻塞。

• clear：将“Flag”设置为False
• set：将“Flag”设置为True

#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
import threading
 
 
def do(event):
    print 'start'
    event.wait()
    print 'execute'
 
 
event_obj = threading.Event()
for i in range(10):
    t = threading.Thread(target=do, args=(event_obj,))
    t.start()
 
event_obj.clear()
inp = raw_input('input:')
if inp == 'true':
    event_obj.set()

 

2.Condition想锁几个就锁几个，使得线程等待，只有满足某条件时，才释放n个线程

import threading


def run(n):
    con.acquire()
    con.wait()
    print("run the thread: %s" % n)
    con.release()


if __name__ == '__main__':

    con = threading.Condition()
    for i in range(10):
        t = threading.Thread(target=run, args=(i,))
        t.start()

    while True:
        inp = input('>>>')
        if inp == 'q':
            break
        con.acquire()
        con.notify(int(inp))
        con.release()

 

线程池

from concurrent.futures import ThreadPoolExecutor

import time
from concurrent.futures import ThreadPoolExecutor


def download(url):
    time.sleep(1)
    print("result:", url)

pool = ThreadPoolExecutor(2)
urls = [
    "www.baidu.com",
    "www.sina.com",
    "www.163.com",
]
for url in urls:
    print("开始请求", url)
    pool.submit(download, url)

print("end")

 

join实例

import threading
import time


def sayhi(num):
    time.sleep(num)
    print("running on number:%s" % num)

if __name__ == '__main__':
    thread_list = []
    for i in range(10):
        t1 = threading.Thread(target=sayhi, args=(i,))
        t1.start()
        thread_list.append(t1)

    for n in thread_list:
        n.join()
    print(threading.active_count())
    print("-------------主线程------------")