一 守护进程
1.1 基本概念
守护进程
- 正常情况下,主进程默认等待子进程调用结束之后结束
- 守护进程在主进程执行代码结束后,自动终止
守护进程语法:
- 进程对象.daemon = True ，设置该进程是守护进程
- 守护进程需要在start()方法之前设置
- 为主进程守护,主进程如果代码执行结束了,该守护进程自动结束.
1.2 基本语法
import os
import time
from multiprocessing import Process
def func():
print("子进程start")
print("子进程end")
p = Process(target=func)
p.start()
print ("主进程执行结束")
执行
[[email protected] python]# python3 test.py 主进程执行结束 子进程start 子进程end
使用守护进程
import os
import time
from multiprocessing import Process
def func():
print("子进程start")
print("子进程end")
p = Process(target=func)
p.daemon = True
p.start()
print ("主进程执行结束")
执行
[[email protected] python]# python3 test.py 主进程执行结束
主进程执行完之后，子进程不在执行
1.3 多个子进程情况
import os
import time
from multiprocessing import Process
def func1():
count = 1
while True:
print ("*" * count)
time.sleep(0.5)
count += 1
def func2():
print("func2 start")
time.sleep(3)
print("func2 end")
p1 = Process(target=func1)
p1.start()
p2 = Process(target=func2)
p2.start()
print ("主进程执行结束")
执行
[[email protected] python]# python3 test.py 主进程执行结束 * func2 start ** *** **** ***** ****** func2 end ******* ******** ********* ********** *********** ************ ************* ************** *************** **************** ***************** ****************** ******************* ******************** ********************* **********************
第一个进程不能结束，设置一个守护进程
import os
import time
from multiprocessing import Process
def func1():
count = 1
while True:
print ("*" * count)
time.sleep(0.5)
count += 1
def func2():
print("func2 start")
time.sleep(3)
print("func2 end")
p1 = Process(target=func1)
p1.daemon = True
p1.start()
p2 = Process(target=func2)
p2.start()
print ("主进程执行结束")
但这种添加还没来得及执行，就被杀掉
执行
[[email protected] python]# python3 test.py 主进程执行结束 func2 start func2 end
当多个子进程并发执行时,默认主进程等待子进程的
如果标记该子进程是守护进程，当主进程执行完所有代码之后,守护进程立刻终止
主进程代码执行到最后一行,就意味着守护进程终止了，其他非守护进程继续执行,主进程仍然会等待他执行结束，最后主进程在真正的释放结束.
1.4 守护进程用途: 报活功能
import os
import time
from multiprocessing import Process
def alive():
while True:
print ("I am the first server,I‘m OK")
time.sleep(0.5)
def func():
print("The first server is used to collect logs")
time.sleep(5) #相当于这个进程存活5s
p1 = Process(target=alive)
p1.daemon = True
p1.start()
p2 = Process(target=func)
p2.start()
#模拟func程序结束，或者服务器宕机,停止保活,这是执行主进程，执行完，则子进程不在执行，即停止报活
p2.join()
print (".......")
执行
[[email protected] python]# python3 test.py I am the first server,I‘m OK The first server is used to collect logs I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK I am the first server,I‘m OK .......
二 lock锁
语法: # 创建一把锁 lock = lock() # 上锁 lock.acquire() # 解锁 lock.release()
2.1 基本用法
import os import time from multiprocessing import Process,Lock lock = Lock() lock.acquire() lock.release() print (111)
执行
[[email protected]node10 python]# python3 test.py 111
死锁 上锁和解锁之间不匹配,只上锁不解锁就是死锁,会产生阻塞;
import os import time from multiprocessing import Process,Lock lock = Lock() lock.acquire() #lock.release() print (111)
执行就会被阻塞，而且不会打印111，成了一把死锁
2.2 模拟一个抢票机制
假设只有一张票
[[email protected] python]# vim ticket
{"count": 1}
抢票方法
import os
import time,json
from multiprocessing import Process,Lock
def wr_info(sign,dic=None):
if sign == "r":
with open("ticket",mode="r",encoding="utf-8") as fp:
dic = json.load(fp)
return dic
elif sign == "w":
with open("ticket",mode="w",encoding="utf-8") as fp:
json.dump(dic,fp)
#抢票方法
def get_ticket(person):
dic = wr_info("r")
time.sleep(0.11)
if dic["count"] > 0:
print("%s抢到票"%(person))
dic["count"] -=1
# 更新数据库
wr_info("w",dic)
else:
print ("%s没有买到票"%(person))
#用ticket来仅从统一调用
def ticket(person):
#查询票数
dic = wr_info("r")
print ("%s查询余票：%s"%(person,dic[‘count‘]))
get_ticket(person)
for i in range(10):
p = Process(target = ticket,args=( "person%s" %(i), ))
p.start()
执行
[[email protected] python]# python3 test.py person0查询余票：1 person1查询余票：1 person2查询余票：1 person3查询余票：1 person4查询余票：1 person5查询余票：1 person6查询余票：1 person7查询余票：1 person8查询余票：1 person9查询余票：1 person3抢到票 person0抢到票 person4抢到票 person5抢到票 person1抢到票 person7抢到票 person2抢到票 person6抢到票 person8抢到票 person9抢到票
发现所有人都抢到票了
2.3 使用锁机制
在主进程创建一把锁，在抢票处上锁，然后再抢完解锁，如下操作
import os
import time,json
from multiprocessing import Process,Lock
def wr_info(sign,dic=None):
if sign == "r":
with open("ticket",mode="r",encoding="utf-8") as fp:
dic = json.load(fp)
return dic
elif sign == "w":
with open("ticket",mode="w",encoding="utf-8") as fp:
json.dump(dic,fp)
#抢票方法
def get_ticket(person):
dic = wr_info("r")
time.sleep(0.11)
if dic["count"] > 0:
print("%s抢到票"%(person))
dic["count"] -=1
# 更新数据库
wr_info("w",dic)
else:
print ("%s没有买到票"%(person))
#用ticket来仅从统一调用
#这里需要把lock传进来
def ticket(person,lock):
#查询票数
dic = wr_info("r")
print ("%s查询余票：%s"%(person,dic[‘count‘]))
lock.acquire()
get_ticket(person)
lock.release()
lock = Lock()
for i in range(10):
p = Process(target = ticket,args=( "person%s" %(i), ))
p.start()
执行
主进程在执行ticket的子进程时，多一个参数
import os
import time,json
from multiprocessing import Process,Lock
def wr_info(sign,dic=None):
if sign == "r":
with open("ticket",mode="r",encoding="utf-8") as fp:
dic = json.load(fp)
return dic
elif sign == "w":
with open("ticket",mode="w",encoding="utf-8") as fp:
json.dump(dic,fp)
#抢票方法
def get_ticket(person):
dic = wr_info("r")
time.sleep(0.11)
if dic["count"] > 0:
print("%s抢到票"%(person))
dic["count"] -=1
# 更新数据库
wr_info("w",dic)
else:
print ("%s没有买到票"%(person))
#用ticket来仅从统一调用
#这里需要把lock传进来
def ticket(person,lock):
#查询票数
dic = wr_info("r")
print ("%s查询余票：%s"%(person,dic[‘count‘]))
lock.acquire()
get_ticket(person)
lock.acquire()
lock = Lock()
for i in range(10):
p = Process(target = ticket,args=( "person%s" %(i), lock))
p.start()
执行
[[email protected] python]# python3 test.py person0查询余票：1 person1查询余票：1 person2查询余票：1 person3查询余票：1 person4查询余票：1 person5查询余票：1 person6查询余票：1 person7查询余票：1 person8查询余票：1 person9查询余票：1 person0抢到票 person1没有买到票 person2没有买到票 person3没有买到票 person4没有买到票 person5没有买到票 person6没有买到票 person7没有买到票 person8没有买到票 person9没有买到票
或者直接加锁
import os
import time,json
from multiprocessing import Process,Lock
def wr_info(sign,dic=None):
if sign == "r":
with open("ticket",mode="r",encoding="utf-8") as fp:
dic = json.load(fp)
return dic
elif sign == "w":
with open("ticket",mode="w",encoding="utf-8") as fp:
json.dump(dic,fp)
#抢票方法
def get_ticket(person):
dic = wr_info("r")
time.sleep(0.11)
if dic["count"] > 0:
print("%s抢到票"%(person))
dic["count"] -=1
#更新数据库
wr_info("w",dic)
else:
print ("%s没有买到票"%(person))
#用ticket来进行统一调用
#这里需要把lock传进来
def ticket(person):
#查询票数
dic = wr_info("r")
print ("%s查询余票：%s"%(person,dic[‘count‘]))
lock.acquire()
#开始抢票
get_ticket(person)
lock.release()
lock = Lock()
for i in range(10):
p = Process(target = ticket,args=( "person%s"%(i),))
p.start()
区分同步和异步
- 在产生进程对象的时候,进程之间是异步的.上锁之后,进程是同步的
- 必须等上一个进程执行完毕之后,下一个进行才能执行,这个是同步.
三 信号量
Semaphore 本质上就是锁,只不过可以控制锁的数量
模拟取钱，假设10个人排队取钱
import os
import time,json
from multiprocessing import Process,Lock,Semaphore
def bank(person):
print ("%s进入柜台取钱"%(person))
print ("%s取完离开"%(person))
for i in range(10):
p = Process(target = bank,args=("person%s"%(i),))
p.start()
执行
[[email protected] python]# python3 test.py person0进入柜台取钱 person0取完离开 person1进入柜台取钱 person1取完离开 person2进入柜台取钱 person2取完离开 person3进入柜台取钱 person3取完离开 person4进入柜台取钱 person4取完离开 person5进入柜台取钱 person5取完离开 person6进入柜台取钱 person6取完离开 person7进入柜台取钱 person7取完离开 person8进入柜台取钱 person8取完离开 person9进入柜台取钱 person9取完离开
假设4个柜台使用semaphore上四把锁
import os
import time,json
from multiprocessing import Process,Lock,Semaphore
def bank(person):
sem.acquire()
time.sleep(5)
print ("%s进入柜台取钱"%(person))
print (os.getpid())
res = os.popen("date").read()
print(res)
sem.release()
print ("%s取完离开"%(person))
sem = Semaphore(4)
for i in range(10):
p = Process(target = bank,args=("person%s"%(i),))
p.start()
执行
person0进入柜台取钱 person3进入柜台取钱 4502 4505 Sat Feb 22 21:58:07 EST 2020 Sat Feb 22 21:58:07 EST 2020 person0取完离开 person3取完离开 person1进入柜台取钱 4503 Sat Feb 22 21:58:07 EST 2020 person1取完离开 person2进入柜台取钱 4504 Sat Feb 22 21:58:07 EST 2020 person2取完离开 person5进入柜台取钱 4507 Sat Feb 22 21:58:12 EST 2020 person5取完离开 person6进入柜台取钱 4508 Sat Feb 22 21:58:12 EST 2020 person6取完离开 person7进入柜台取钱 person4进入柜台取钱 4506 4509 Sat Feb 22 21:58:12 EST 2020 person4取完离开 Sat Feb 22 21:58:12 EST 2020 person7取完离开 person8进入柜台取钱 4510 Sat Feb 22 21:58:17 EST 2020 person8取完离开 person9进入柜台取钱 4511 Sat Feb 22 21:58:17 EST 2020 person9取完离开
根据时间，每次四个一次
四 事件
4.1 基本概念
阻塞事件 ：
- e = Event()生成事件对象e
- e.wait()动态给程序加阻塞 , 程序当中是否加阻塞完全取决于该对象中的is_set()
[默认返回值是False]
- 如果是True 不加阻塞
- 如果是False 加阻塞
控制这个属性的值
- set()方法 将这个属性的值改成True
- clear()方法 将这个属性的值改成False
- is_set()方法 判断当前的属性是否为True (默认上来是False)
4.2 基本语法
默认时False
from multiprocessing import Process,Event e = Event() print (e.is_set())
执行
[[email protected] python]# python3 test.py False
使用阻塞
from multiprocessing import Process,Event
e = Event()
print (e.is_set())
e.wait(5) #相当于sleep
print ("事件")
执行
[[email protected] python]# python3 test.py False 事件
set
from multiprocessing import Process,Event
e = Event()
e.set()
print (e.is_set())
e.wait()
print ("事件")
执行，直接打印
[[email protected] python]# python3 test.py True #不加阻塞 事件
Claen
e = Event() # True e.set() e.wait() print(123) e.clear() # False e.wait() print(456)
执行，456不会打印，因为clean后时False
[[email protected] python]# python3 test.py 123
4.3 模拟红绿灯效果
from multiprocessing import Process,Event
import time
def traffic_light(e):
#默认红灯先亮
print ("red")
while True:
if e.is_set():
#当前时绿灯
time.sleep(2)
#等完2秒，变红灯
print("red")
e.clear()
else:
#当前时红灯
time.sleep(2)
#等完2秒，变绿灯
print ("blue")
e.set()
e = Event()
traffic_light(e)
执行
[[email protected] python]# python3 test.py red blue red blue red
模拟车辆遇到红灯停，绿灯行
from multiprocessing import Process,Event
import time,random
def traffic_light(e):
#默认红灯先亮
print ("red")
while True:
if e.is_set():
#当前时绿灯
time.sleep(2)
#等完2秒，变红灯
print("red")
e.clear()
else:
#当前时红灯
time.sleep(2)
#等完2秒，变绿灯
print ("blue")
e.set()
def car(e,i):
if not e.is_set():
print ("The car%s is wait"%(i))
e.wait()
print("car%s is running"%(i))
e = Event()
p1 = Process(target=traffic_light,args=(e,))
p1.start()
for i in range(20):
time.sleep(random.uniform(0,2))
p2 = Process(target=car,args = (e,i))
p2.start()
执行
[[email protected] python]# python3 test.py red The car0 is wait blue car0 is running car1 is running red The car2 is wait blue car2 is running car3 is running car4 is running red The car5 is wait blue car5 is running car6 is running red The car7 is wait The car8 is wait The car9 is wait The car10 is wait blue car10 is running car8 is running car9 is running car7 is running car11 is running red The car12 is wait blue car12 is running car13 is running car14 is running red The car15 is wait The car16 is wait blue car15 is running car16 is running car17 is running car18 is running red The car19 is wait blue car19 is running red
4.4 使用守护进程
from multiprocessing import Process,Event
import time,random
def traffic_light(e):
#默认红灯先亮
print ("red")
while True:
if e.is_set():
#当前时绿灯
time.sleep(2)
#等完2秒，变红灯
print("red")
e.clear()
else:
#当前时红灯
time.sleep(2)
#等完2秒，变绿灯
print ("blue")
e.set()
def car(e,i):
if not e.is_set():
print ("The car%s is wait"%(i))
e.wait()
print("car%s is running"%(i))
e = Event()
p1 = Process(target=traffic_light,args=(e,))
p1.daemon = True
p1.start()
for i in range(20):
time.sleep(random.uniform(0,2))
p2 = Process(target=car,args = (e,i))
p2.start()
执行
red The car0 is wait The car1 is wait The car2 is wait blue car0 is running car1 is running car2 is running car3 is running car4 is running car5 is running car6 is running red The car7 is wait The car8 is wait The car9 is wait The car10 is wait blue car8 is running car7 is running car9 is running car10 is running car11 is running red The car12 is wait blue car12 is running car13 is running car14 is running red The car15 is wait blue car15 is running car16 is running car17 is running red The car18 is wait The car19 is wait
卡在这里不执行，是因为car已经跑完，进程不再执行，卡在e.wait这里
使用join
from multiprocessing import Process,Event
import time,random
def traffic_light(e):
#默认红灯先亮
print ("red")
while True:
if e.is_set():
#当前时绿灯
time.sleep(2)
#等完2秒，变红灯
print("red")
e.clear()
else:
#当前时红灯
time.sleep(2)
#等完2秒，变绿灯
print ("blue")
e.set()
def car(e,i):
if not e.is_set():
print ("The car%s is wait"%(i))
e.wait()
print("car%s is running"%(i))
e = Event()
lst = []
p1 = Process(target=traffic_light,args=(e,))
p1.daemon = True
p1.start()
for i in range(20):
time.sleep(random.uniform(0,2))
p2 = Process(target=car,args = (e,i))
p2.start()
lst.append(p2)
for i in lst:
i.join()
print("程序彻底结束;")
执行
red The car0 is wait The car1 is wait blue car1 is running car0 is running car2 is running car3 is running red The car4 is wait blue car4 is running car5 is running car6 is running car7 is running red The car8 is wait The car9 is wait blue car9 is running car8 is running car10 is running red The car11 is wait blue car11 is running car12 is running car13 is running car14 is running red The car15 is wait blue car15 is running car16 is running car17 is running red The car18 is wait The car19 is wait blue car19 is running car18 is running 程序彻底结束;
原文地址：https://www.cnblogs.com/zyxnhr/p/12354445.html
时间： 2024-08-03 14:27:39