开启进程 守护进程

一:开启进程的方式 第一种

from multiprocessing import Process
import time
def task(name):
    print(f"{name} is running ")
    time.sleep(3)
    print(f"{name} is gone")
if __name__ == '__main__':
    p = Process(target = task,args = ('常鑫',))
    p.start()
    print('===主')

    ===主
常鑫 is running
常鑫 is gone

开启进程的方式 第二种

from multiprocessing import Process
import time
class MyProcess(Process):
    def __init__(self,name):
        super().__init__()
        self.name =name
    def run(self):
        print(f"{self.name} is running")
        time.sleep(2)
        print(f"{self.name} is gone")
if __name__ == '__main__':
    p = MyProcess('常鑫')
    p.start()
    print('=====主')
'''
=====主
常鑫 is running
常鑫 is gone

'''

开启进程的简单应用

串行的执行结果

from multiprocessing import Process
import time
def task(name):
    print(f"{name} is running")
    time.sleep(1)
    print(f"{name} is gone")
def task1(name):
    print(f"{name} is rinning")
    time.sleep(2)
    print(f"{name} is gone")
def task2(name):
    print(f"{name} is running")
    time.sleep(3)
    print(f"{name} is gone")

if __name__ == '__main__':
    p1 = Process(target = task ,args = ('常鑫',))
    p2 = Process(target = task,args = ('李业',))
    start_time = time.time()
    #  一个进程串行的执行三个任务
    task('常鑫')
    task1('李业')
    task2('海狗')
    print(f"子进程:{time.time() - start_time}")
''''
常鑫 is running
常鑫 is gone
李业 is rinning
李业 is gone
海狗 is running
海狗 is gone
子进程:6.009300947189331

三个程序并发或者并行的执行三个任务

from multiprocessing import Process
import time
def task(name):
    print(f"{name} is running")
    time.sleep(1)
    print(f"{name} is gone")
def task1(name):
    print(f"{name} is rinning")
    time.sleep(2)
    print(f"{name} is gone")
def task2(name):
    print(f"{name} is running")
    time.sleep(3)
    print(f"{name} is gone")

if __name__ == '__main__':
    p1 = Process(target = task ,args = ('常鑫',))
    p2 = Process(target = task,args = ('李业',))
    start_time = time.time()
    p1.start()
    p2.start()
    task2('海狗')
    print(f"结束时间{time.time() - start_time}")
''''
海狗 is running
常鑫 is running
李业 is running
常鑫 is gone
李业 is gone
海狗 is gone
结束时间3.014525890350342
'''

验证昨天的结论 :

1. 子进程必须依赖于主进程
2. 子进程 copy 了主进程
3. 子进程开辟进程,开销比较大,所以开的比较慢

二 : 进程 pid

如何区分内存中的这些进程?

命令获取所有进程的 pid windows 是 tasklist Mac是ps aux

还有一个 ps — ef

代码级别获取 pid

import os
print(os.getpid())

如何获取父进程

import os
print(os.getppid())

三 : 验证进程之间的空间隔离

不可变数据类型的时候

from multiprocessing import Process
import time
import os
name = '太白'
def task():
    global name
    name = "刚子sb"
    print(name)
if __name__ == '__main__':
    p = Process(target = task)
    p.start()
    time.sleep(3)        # 睡了一下,所以先执行子进程
    print(f"主:{name}")
#  不可变数据类型时,子进程和父进程之间是隔离的,二者毫不影响
# 刚子sb
# 主:太白

我们来看一下可变数据类型

无论子进程中如何操作,在主进程中都是不变的

from multiprocessing import Process
import time
lst = ['丽丽']
def task():
    lst.append("怼姐")
    print(f"子进程{lst}")
if __name__ == '__main__':
    p = Process(target = task)
    p.start()
    # time.sleep(3)
    # 加不加这个结果  完全不同 加了这个先输出子进程
    print(f'主{lst}')

    子进程['丽丽', '怼姐']
主['丽丽']

总结:无论是可变数据类型,还是不可变数据类型,子进程的操作对主进程都没有影响

四 : join : 让主进程等待子进程执行结束,再执行主进程

这个怎么说呢? join 就是阻塞主进程有 join 主进程下方的代码一律不执行,直到执行完毕,但是一定切记,在开始的时候是并发的,消耗的时间也是记录在这个里面

from multiprocessing import Process
import time
def task(name):
    print(f"{name} is running")
    time.sleep(2)
    print(f"{name} is gone")
if __name__ == '__main__':
    p = Process(target = task,args = ('魏无羡',))
    p.start()
    p.join()
    print('===主')
'''
魏无羡 is running
魏无羡 is gone
===主
'''
先执行子进程,然后再执行主进程

多个子进程使用 join

from multiprocessing import Process
import time
def task(name,sec):
    print(f"{name} is running")
    time.sleep(1)
    print(f'{name} is gone')
if __name__ == '__main__':
    start_time = time.time()
    p1 = Process(target = task,args = ('魏无羡',1))
    p2 = Process(target = task,args = ('蓝忘机',2))
    p3 = Process(target = task,args = ('蓝曦臣',3))
    p1.start()
    p2.start()
    p3.start()
    print(f"主进程:{time.time() - start_time}")
''''
魏无羡 is running
主进程:0.009562253952026367  只是主进程运行的时间
蓝忘机 is running
蓝曦臣 is running
魏无羡 is gone
蓝忘机 is gone
蓝曦臣 is gone
'''

下面的两个验证要好好弄明白

验证一

from multiprocessing import Process
import time
def task(name,sec):
    print(f"{name} is running")
    time.sleep(1)
    print(f'{name} is gone')
if __name__ == '__main__':
    start_time = time.time()
    p1 = Process(target = task,args = ('魏无羡',1))
    p2 = Process(target = task,args = ('蓝忘机',2))
    p3 = Process(target = task,args = ('蓝曦臣',3))
    p1.start()
    p2.start()
    p3.start()

    p1.join()
    p2.join()
    p3.join()
    print(f"主进程:{time.time() - start_time}")

'''
魏无羡 is running
蓝忘机 is running
蓝曦臣 is running
魏无羡 is gone
蓝忘机 is gone
蓝曦臣 is gone
主进程:1.0214881896972656
'''

验证二

from multiprocessing import Process
import time

def task(name,sec):
    print(f'{name}is running')
    time.sleep(sec)
    print(f'{name} is gone')

if __name__ == '__main__':
    start_time = time.time()
    p1 = Process(target=task,args=('常鑫',1))
    p2 = Process(target=task,args=('李业',2))
    p3 = Process(target=task,args=('海狗',3))

    p1.start()
    p2.start()
    p3.start()
    # join就是阻塞

    p1.join()
    print(f'==主1:{time.time()-start_time}')
    p2.join()
    print(f'===主2:{time.time()-start_time}')
    p3.join()
    print(f'==主3:{time.time()-start_time}')  

'''
常鑫is running
李业is running
海狗is running
常鑫 is gone
==主1:1.0072300434112549
李业 is gone
===主2:2.0071139335632324
海狗 is gone
==主3:3.0082600116729736
'''

当然还有精简代码

from multiprocessing import Process
import time

def task(sec):
    print(f'is running')
    time.sleep(sec)
    print(f' is gone')

if __name__ == '__main__':
    start_time = time.time()
    l1 = []
    for i in range(1, 4):
        p = Process(target=task,args=(i,))
        l1.append(p)
        p.start()

    for i in l1:
        i.join()

    print(f'==主{time.time()-start_time}')
'''
is running
is running
is running
 is gone
 is gone
 is gone
==主3.013340950012207
'''

五 : 进程的其他参数

terminate 还有p.is_alive( ) 没被杀死返回 True 杀死之后返回 False

执行这个杀死的进程,加睡眠时间 或者是 join 给点缓存时间

args 默认返回值: Process-1

from multiprocessing import Process
import time

def task(name):
    print(f'{name} is running')
    time.sleep(2)
    print(f'{name} is gone')
if __name__ == '__main__':
    p = Process(target=task,args=('常鑫',),)  # 加上返回的就是 alex  不加返回的是Process-1
    p.start()
    print(p.name)
    print('==主开始')

六 : 守护进程

守护进程:

古时候 太监守护这个皇帝,如果皇帝驾崩了,太监直接也就死了.

子进程守护着主进程,只要主进程结束,子进程跟着就结束,

from multiprocessing import Process
import time

def task(name):
    print(f'{name} is running')
    time.sleep(2)
    print(f'{name} is gone')
if __name__ == '__main__':
    # 在windows环境下, 开启进程必须在 __name__ == '__main__' 下面
    p = Process(target=task,args=('常鑫',))  # 创建一个进程对象
    p.daemon = True  # 将p子进程设置成守护进程,只要主进程结束,守护进程马上结束.
    p.start()
    # p.daemon = True  # 一定要在子进程开启之前设置
    time.sleep(1)
    print('===主')
'''
常鑫 is running
===主

'''

原文地址：https://www.cnblogs.com/hualibokeyuan/p/11384612.html