线程,协程

1. 线程的创建.

#线程的创建
from threading import Thread
import time
def sayhi(name):
    time.sleep(2)
    print("%s say hello"%name)

if __name__ =="__main__":
    t =Thread(target=sayhi,args =("egon",))
    t.start()
    print("主线程")

2.基于类创建线程

#通过类去创建线程.
from threading import Thread
import time
class Sayhi(Thread):
    def __init__(self,name):
        super().__init__()
        self.name =name

    def run(self):
        time.sleep(2)
        print("%s say hello"%self.name)

if __name__ == '__main__':
    t =Sayhi("egon")
    t.start()
    print("主线程")

打印结果：

主线程 （两秒后往下执行）
egon say hello

3. 多线程与多进程.

from threading import Thread
from multiprocessing import Process
import os,time
def work():
    print("hello",os.getpid())



if __name__ == '__main__':
    #part1:在主进程下开启多个线程,每个线程都跟主进程pid一样
    t1 =Thread(target=work)
    t2 =Thread(target=work)
    t1.start()
    t2.start()
    print("主线程/主进程pid",os.getpid())


    #part2:开启多个进程，每个进程都有不同的pid
    p1 =Process(target=work)
    p2 =Process(target=work)
    p1.start()
    p2.start()
    print("主线程/主进程pid",os.getpid())

　　

线程的属性

Thread实例对象的方法
  # isAlive(): 返回线程是否活动的。
  # getName(): 返回线程名。
  # setName(): 设置线程名。

threading模块提供的一些方法：
  # threading.currentThread(): 返回当前的线程变量。
  # threading.enumerate(): 返回一个包含正在运行的线程的list。正在运行指线程启动后、结束前，不包括启动前和终止后的线程。
  # threading.activeCount(): 返回正在运行的线程数量，与len(threading.enumerate())有相同的结果。

　案例

from threading import Thread
import threading
from multiprocessing import Process
import os

def work():
    import time
    time.sleep(3)
    print(threading.current_thread().getName())


if __name__ == '__main__':
    #在主进程下开启线程
    t=Thread(target=work)
    t.start()

    print(threading.current_thread().getName())
    print(threading.current_thread()) #主线程
    print(threading.enumerate()) #连同主线程在内有两个运行的线程
    print(threading.active_count())
    print('主线程/主进程')


打印结果：
MainThread
<_MainThread(MainThread, started 104508)>
[<_MainThread(MainThread, started 104508)>, <Thread(Thread-1, started 102040)>]
2
主线程/主进程
Thread-1

　　

join方法

from threading import Thread
import time
def sayhi(name):
    time.sleep(2)
    print('%s say hello' %name)

if __name__ == '__main__':
    t=Thread(target=sayhi,args=('egon',))
    t.start()
    t.join()
    print('主线程')
    print(t.is_alive())
    '''
    egon say hello
    主线程
    False
    '''

　打印结果： 三行代码经过2秒同时打印出来,(如果把join去掉的话，先打印主线程 ，然后记过两秒打印子线程.)

egon say hello
主线程
False

守护线程案例

from threading import Thread
import time
def sayhi(name):
    time.sleep(2)
    print('%s say hello' %name)

if __name__ == '__main__':
    t=Thread(target=sayhi,args=('egon',))
    t.setDaemon(True) #必须在t.start()之前设置  ,这段代码还没来得及子线程执行就已经结束了，所以只打印了结果的输出
    t.start()
    print('主线程')
    print(t.is_alive())

打印结果：
延时两秒打印如下内容
主线程
True

　　

协程:

from greenlet import greenlet

def eat():
    print("eat start")
    g2.switch()
    print("eating end")
    g2.switch()

def play():
    print("play start")
    g1.switch()
    print("play end")

g1 =greenlet(eat)
g2 =greenlet(play)
g1.switch()

　　

from gevent import  monkey;monkey.patch_all()
import time
import gevent

def task():
    time.sleep(1)
    print(12345)

def sync():
    for i in range(10):
        task()


def async():
    g_lst =[]
    for i in range(10):
        g =gevent.spawn(task)
        g_lst.append(g)
    gevent.joinall(g_lst) # for g in g_lst:g.join()
sync()
async()

　打印结果： 前十个12345 一个一个输出，后10个一次性输出.

12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345
12345

协程案例。

import time
import gevent
def eat():
    print("eating start")
    time.sleep(1)
    print("eating end")


def play():
    print("playing start")
    time.sleep(1)
    print("playing end")

g1 =gevent.spawn(eat)
g2 =gevent.spawn(play)
g1.join()
g2.join()

协程的应用

from gevent import monkey;monkey.patch_all()
import gevent
import requests
import time

def get_page(url):
    print('GET: %s' %url)
    response=requests.get(url)
    if response.status_code == 200:
        print('%d bytes received from %s' %(len(response.text),url))


start_time=time.time()
gevent.joinall([
    gevent.spawn(get_page,'https://www.python.org/'),
    gevent.spawn(get_page,'https://www.yahoo.com/'),
    gevent.spawn(get_page,'https://github.com/'),
])
stop_time=time.time()
print('run time is %s' %(stop_time-start_time))