python:协程

Posted 2020-10-23 CanSun

#协程，又称为微线程，是一种用户态的轻量级线程

#!usr/bin/env python
# -*- coding:utf-8 -*-

__author__ = "Samson"
#greenlet是协程"手动挡切换"
from greenlet import greenlet

def test1():
    print(12)
    t2.switch()#切换到协程t2
    print(36)
    t2.switch()

def test2():
    print(48)
    t1.switch()
    print(60)

t1 = greenlet(test1)#启动一个协程
t2 = greenlet(test2)

t1.switch()

#!usr/bin/env python
# -*- coding:utf-8 -*-

__author__ = "Samson"
#greenlet是协程"自动挡切换"
import gevent

def foo():
    print("Running in foo")
    gevent.sleep(2)#模仿io操作
    print("Explicit context switch to foo again")


def bar():
    print("Explicit精确的 context内容 to bar")
    gevent.sleep(1)  # 模仿io操作
    print("Implicit context switch back to bar")

    gevent.joinall([
        gevent.spawn(foo),
        gevent.spawn(bar),
    ])


协程之爬虫

#!usr/bin/env python
# -*- coding:utf-8 -*-

__author__ = "Samson"

from urllib import request
import gevent,time
from gevent import monkey

monkey.patch_all()#将当前所有程序io操作单独做上标记，这样才能用协程方式进行爬虫，否则将会是串行的

def f(url):
    print("Get: %s" %url)
    resp = request.urlopen(url)
    data = resp.read()
    print("%d bytes received from %s."%(len(data),url))

urls = ["https://www.python.org/",
    "https://www.yahoo.com/",
    "https://github.com/"]
time_start = time.time()
for url in urls:
    f(url)
print("同步cost",time.time()-time_start)

async_time_start = time.time()
gevent.joinall([
    gevent.spawn(f,"https://www.python.org/"),
    gevent.spawn(f,"https://www.yahoo.com/"),
    gevent.spawn(f,"https://github.com/"),
])
print("协程cost",time.time()-async_time_start)