标签：har next toc ndt roo res ++ logo copy
初始化生成器函数 返回生成器对象,简称生成器
def gen(): for i in range(10): #yield 返回便能够保留状态 yield i mygen = gen() for i in mygen: print(i)
执行
[root@node10 python]# python3 test.py 0 1 2 3 4 5 6 7 8 9
使用next定义遍历里次数
def gen(): for i in range(10): yield i # 初始化生成器函数 返回生成器对象,简称生成器 mygen = gen() for i in range (3): res = next(mygen) print (res)
执行
[root@node10 python]# python3 test.py 0 1 2
def producer(): for i in range(100): yield i def consumer(): g = producer() for i in g: print(i) consumer()
switch 一般遇到阻塞时,可以手动调用该函数进行任务切换
缺点:不能够自动规避io,即不能自动实现遇到阻塞就切换
from greenlet import greenlet import time def plane(): print ("plane one") print ("Plane two") def fly(): print ("fly to newyork") print ("fly to beijing") g1 = greenlet(plane) g2 = greenlet(fly) g1.switch()
在执行之前，需要安装greenlet模块
[root@node10 python]# pip-3 install wheel
[root@node10 python]# pip-3 install gevent
执行python
[root@node10 python]# python3 test.py plane one Plane two
添加阻塞，并配置一个swith
import time def plane(): print ("plane one") g2.switch() time.sleep(2) print ("Plane two") def fly(): print ("fly to newyork") time.sleep(2) print ("fly to beijing") g1 = greenlet(plane) g2 = greenlet(fly) g1.switch()
执行
[root@node10 python]# python3 test.py plane one fly to newyork fly to beijing
有阻塞不能启动切换
from greenlet import greenlet import time def plane(): print ("plane one") g2.switch() time.sleep(2) print ("Plane two") def fly(): print ("fly to newyork") time.sleep(2) print ("fly to beijing") g1.switch() g1 = greenlet(plane) g2 = greenlet(fly) g1.switch()
执行
[root@node10 python]# python3 test.py plane one fly to newyork fly to beijing Plane two
缺陷:不能够识别time.sleep 阻塞
from greenlet import greenlet import gevent import time def plane(): print ("plane one") time.sleep(2) print ("Plane two") def fly(): print ("fly to newyork") time.sleep(2) print ("fly to beijing") # 利用gevent 创建协程对象g1 g1 = gevent.spawn(plane) # 利用gevent 创建协程对象g2 g2 = gevent.spawn(fly) g1.join() #阻塞,直到g1协程任务执行完毕 g2.join() #阻塞,直到g2协程任务执行完毕 print("主线程执行完毕")
执行
[root@node10 python]# python3 test.py plane one Plane two fly to newyork fly to beijing 主线程执行完毕
阻塞没有生效
进阶改造
from greenlet import greenlet import gevent import time def plane(): print ("plane one") gevent.sleep(2) print ("Plane two") def fly(): print ("fly to newyork") gevent.sleep(2) print ("fly to beijing") # 利用gevent 创建协程对象g1 g1 = gevent.spawn(plane) # 利用gevent 创建协程对象g2 g2 = gevent.spawn(fly) g1.join() #阻塞,直到g1协程任务执行完毕 g2.join() #阻塞,直到g2协程任务执行完毕 print("主线程执行完毕")
执行，自动实现任务切换
[root@node10 python]# python3 test.py plane one fly to newyork Plane two fly to beijing 主线程执行完毕
终极解决不识别问题
下面所有引入的模块所包含的阻塞,重新识别出来.
from greenlet import greenlet from gevent import monkey monkey.patch_all() import gevent import time def plane(): print ("plane one") time.sleep(2) print ("Plane two") def fly(): print ("fly to newyork") time.sleep(2) print ("fly to beijing") # 利用gevent 创建协程对象g1 g1 = gevent.spawn(plane) # 利用gevent 创建协程对象g2 g2 = gevent.spawn(fly) g1.join() #阻塞,直到g1协程任务执行完毕 g2.join() #阻塞,直到g2协程任务执行完毕 print("主线程执行完毕")
执行
[root@node10 python]# python3 test.py plane one fly to newyork Plane two fly to beijing 主线程执行完毕
oinall value函数的用法
rom gevent import monkey;monkey.patch_all() import time import gevent def plane(): print ("plane one") time.sleep(2) print ("Plane two") return ("有两架飞机") def fly(): print ("fly to newyork") time.sleep(2) print ("fly to beijing") return ("fly two place") g1 = gevent.spawn(plane) g2 = gevent.spawn(fly) gevent.joinall( [g1,g2] ) # 获取协成的返回值 print(g1.value) print(g2.value) print("主线程执行完毕")
执行
plane one
fly to newyork
Plane two
fly to beijing
有两架飞机
fly two place
主线程执行完毕
利用协程爬取页面数据
安装request模块
[root@node10 python]# pip-3 install requests
import gevent import requests import time # 抓取网站信息,返回响应对象 print ("<++++++++++++抓取网站信息,返回响应对象+++++++++++++++++>") response = requests.get("http://www.baidu.com") print(response) # 获取状态码 print ("<++++++++++++获取状态码+++++++++++++++++>") res = response.status_code print(res) # 获取字符编码集 apparent_encoding print ("<++++++++++++获取字符编码集 apparent_encoding+++++++++++++++++>") res_code = response.apparent_encoding print(res_code) # 设置编码集 print ("<++++++++++++++设置编码集+++++++++++++++++>") response.encoding = res_code print ("<++++++++++++获取网页里面的内容+++++++++++++++++>") res = response.text print(res) import re strvar = r‘<img hidefocus=true src="https://www.baidu.com/img/bd_logo1.png" width=270 height=129>‘ obj = re.search("src=(.*?) ",strvar) res = obj.group() print (res) res = obj.groups() print (res) res = obj.groups()[0] print (res)
执行
<++++++++++++抓取网站信息,返回响应对象+++++++++++++++++> <Response [200]> <++++++++++++获取状态码+++++++++++++++++> 200 <++++++++++++获取字符编码集 apparent_encoding+++++++++++++++++> utf-8 <++++++++++++++设置编码集+++++++++++++++++> <++++++++++++获取网页里面的内容+++++++++++++++++> <!DOCTYPE html> <!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer><link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css><title>百度一下，你就知道</title></head> <body link=#0000cc> <div id=wrapper> <div id=head> <div class=head_wrapper> <div class=s_form> <div class=s_form_wrapper> <div id=lg> <img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129> </div> <form id=form name=f action=//www.baidu.com/s class=fm> <input type=hidden name=bdorz_come value=1> <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden name=rsv_bp value=1> <input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span class="bg s_ipt_wr"><input id=kw name=wd class=s_ipt value maxlength=255 autocomplete=off autofocus></span><span class="bg s_btn_wr"><input type=submit id=su value=百度一下 class="bg s_btn"></span> </form> </div> </div> <div id=u1> <a href=http://news.baidu.com name=tj_trnews class=mnav>新闻</a> <a href=http://www.hao123.com name=tj_trhao123 class=mnav>hao123</a> <a href=http://map.baidu.com name=tj_trmap class=mnav>地图</a> <a href=http://v.baidu.com name=tj_trvideo class=mnav>视频</a> <a href=http://tieba.baidu.com name=tj_trtieba class=mnav>贴吧</a> <noscript> <a href=http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1 name=tj_login class=lb>登录</a> </noscript> <script>document.write(‘<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=‘+ encodeURIComponent(window.location.href+ (window.location.search === "" ? "?" : "&")+ "bdorz_come=1")+ ‘" name="tj_login" class="lb">登录</a>‘);</script> <a href=//www.baidu.com/more/ name=tj_briicon class=bri style="display: block;">更多产品</a> </div> </div> </div> <div id=ftCon> <div id=ftConw> <p id=lh> <a href=http://home.baidu.com>关于百度</a> <a href=http://ir.baidu.com>About Baidu</a> </p> <p id=cp>©2017 Baidu <a href=http://www.baidu.com/duty/>使用百度前必读</a> <a href=http://jianyi.baidu.com/ class=cp-feedback>意见反馈</a> 京ICP证030173号 <img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html> src="https://www.baidu.com/img/bd_logo1.png" (‘"https://www.baidu.com/img/bd_logo1.png"‘,) "https://www.baidu.com/img/bd_logo1.png"
爬虫实例
import gevent import requests import time # 抓取网站信息,返回响应对象 response = requests.get("http://www.baidu.com") print(response) # 获取状态码 res = response.status_code print(res) # 获取字符编码集 apparent_encoding res_code = response.apparent_encoding print(res_code) # 设置编码集 response.encoding = res_code res = response.text print(res) url_list = [ "http://www.baidu.com", "http://www.4399.com", "http://www.7k7k.com", "http://www.jingdong.com", "http://www.taobao.com", ] def get_url(url): response = requests.get(url) if response.status_code == 200: pass # print(response.text) # (1) 正常方式爬取数据 startime = time.time() for i in url_list: get_url(i) endtime = time.time() print("<=1=1=1=1=1=1=1=1=>") print(endtime-startime) # (2) 用协程爬取数据 更快 startime = time.time() lst = [] for i in url_list: g = gevent.spawn(get_url,i) lst.append(g) gevent.joinall(lst) endtime = time.time() print("<=2=2=2=2=2=2=2=2=2=>") print(endtime - startime)
执行
<Response [200]> 200 utf-8 <!DOCTYPE html> <!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer><link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css><title>百度一下，你就知道</title></head> <body link=#0000cc> <div id=wrapper> <div id=head> <div class=head_wrapper> <div class=s_form> <div class=s_form_wrapper> <div id=lg> <img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129> </div> <form id=form name=f action=//www.baidu.com/s class=fm> <input type=hidden name=bdorz_come value=1> <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden name=rsv_bp value=1> <input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span class="bg s_ipt_wr"><input id=kw name=wd class=s_ipt value maxlength=255 autocomplete=off autofocus></span><span class="bg s_btn_wr"><input type=submit id=su value=百度一下 class="bg s_btn"></span> </form> </div> </div> <div id=u1> <a href=http://news.baidu.com name=tj_trnews class=mnav>新闻</a> <a href=http://www.hao123.com name=tj_trhao123 class=mnav>hao123</a> <a href=http://map.baidu.com name=tj_trmap class=mnav>地图</a> <a href=http://v.baidu.com name=tj_trvideo class=mnav>视频</a> <a href=http://tieba.baidu.com name=tj_trtieba class=mnav>贴吧</a> <noscript> <a href=http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1 name=tj_login class=lb>登录</a> </noscript> <script>document.write(‘<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=‘+ encodeURIComponent(window.location.href+ (window.location.search === "" ? "?" : "&")+ "bdorz_come=1")+ ‘" name="tj_login" class="lb">登录</a>‘);</script> <a href=//www.baidu.com/more/ name=tj_briicon class=bri style="display: block;">更多产品</a> </div> </div> </div> <div id=ftCon> <div id=ftConw> <p id=lh> <a href=http://home.baidu.com>关于百度</a> <a href=http://ir.baidu.com>About Baidu</a> </p> <p id=cp>©2017 Baidu <a href=http://www.baidu.com/duty/>使用百度前必读</a> <a href=http://jianyi.baidu.com/ class=cp-feedback>意见反馈</a> 京ICP证030173号 <img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html> <=1=1=1=1=1=1=1=1=> 14.512077331542969 <=2=2=2=2=2=2=2=2=2=> 6.321309566497803
协程的速度比较快
标签：har next toc ndt roo res ++ logo copy
原文地址：https://www.cnblogs.com/zyxnhr/p/12382826.html
