并发编程 ~~~ 多进程~~~进程创建的两种方式, 进程pid, 验证进程之间的空间隔离, 进程对象join方法, 进程对象其他属性

一 进程创建的两种方式

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',))
    p.start()
    print('主进程开始')
    time.sleep(3)   
    print('主进程结束')

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()   # 启动的是类里面的run方法
    print('主进程')

二 进程pid

import os
import time
print(f'子进程:{os.getpid()}')
print(f'主(父)进程:{os.getppid()}')
time.sleep(50)

三 验证进程之间的空间隔离

from multiprocessing import Process
import time
name = '小虎'
lst = [1,2,3]
def task():
    global name
    name = '海狗'
    lst.append(4)
    print(f'子进程{name}')
    print(f'子进程{lst}')

if __name__ == '__main__':
    p = Process(target=task)
    p.start()
    time.sleep(2)
    print(f'主进程{name}')
    print(f'主进程{lst}')
# 子进程海狗
# 子进程[1, 2, 3, 4]
# 主进程小虎
# 主进程[1, 2, 3]

主进程和子进程之间是隔离的

四 进程对象join方法

join让主进程等待子进程结束之后,在执行主进程.

from multiprocessing import Process
import time
def task(sec):
    print('running')
    time.sleep(sec)
    print('gone')

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

    p1.start()
    p2.start()
    p3.start()

    p1.join()
    p2.join()
    p3.join()

    print(time.time() - start_time)
# 优化上面代码:
    lst =[]
    for i in range(1,4):
        p = Process(target=task,args=(i,))
        lst.append(p)
        p.start()
    for k in lst:
        k.join()

    print(time.time() - start_time)

五 进程对象其他属性

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=('大黑',),name='进程1')
    p.start()
    time.sleep(1)
    p.terminate() # 杀死子进程
    p.join() # 让主进程等待子进程结束之后,在执行主进程.
    print(p.is_alive()) # 判断子进程是不是还在运行
    print(p.name) # 进程的名字
    p.name = '小虎'
    print(p.name)
    print('主进程')