python_ concurrent programming - multi-process

from multiprocessing Import Process
 Import os 

DEF func1 ():
     Print ( ' sub-process 1 ' , os.getpid ())    # child process: Get the current process of process ID 
    Print ( ' the parent process child process: ' , os.getppid ( )) # get the process of the parent process the above mentioned id 
DEF func2 ():
     Print ( ' sub-process 2 ' , os.getpid ())
     Print ( ' the parent process child process: ' , os.getppid ())
 DEF func3 ():
     Print ( ' sub-process 3 ', os.getpid ())
     Print ( ' the parent process child process: ' , os.getppid ()) 

IF  __name__ == ' __main__ ' : 
    p1 = Process (target = func1)   # Registration: The name of the function (memory address) Sign into child processes 
    P2 = process (target = func2)   # p1 is a process object 
    p3 = process (target = func3) 
    p1.start ()   # open a child process 
    p2.start ()   # three parallel sub-processes 
    p3 .start ()
     Print ( ' parent: ' , os.getpid ())   # parent: get the process ID of the current process 
    Print ( ': Parent process of the parent process ' , os.getppid ()) # parent process id acquisition process

　　The order of execution of the child process will change, indicating that the three sub-processes in parallel.

 

　　The arguments:

from multiprocessing Import Process
 Import OS 

DEF func1 (args):     # args reception parameters 
    Print ( ' . 1 sub-process ' , os.getpid ())    # child process: the process acquires the current process number 
    Print ( ' parent child process: ' , os.getppid ()) # get the process of the parent process the above mentioned id 
    Print (args)      # print parameters passed in 


IF  __name__ == ' __main__ ' : 
    p1 = process (target = func1, args = ( ' parameter ' ,))    #Passed as a tuple of parameters, if only to pass a parameter must be a comma 
    p1.start ()
     Print ( ' parent: ' , os.getpid ())   # parent: Get the current process of process ID 
    Print ( ' : parent process of the parent process ' , os.getppid ()) # parent process id acquisition process

result:

 

　　Open multiple child process method:

from multiprocessing Import Process 

DEF func1 (args):
     Print ( ' * ' * args) 

IF  the __name__ == ' __main__ ' :
     # may be used to achieve open loop for a plurality of sub-processes 
    for I in Range (l, 5 ): 
        P1 = Process ( = func1 target, args = (I,)) 
        p1.start ()

Result 1: 　　Result 2:

 

 　　Multi-process join () method:

from multiprocessing Import Process 

DEF func1 (args):
     Print ( ' sub-process. 1 ' )
     Print (args) 

IF  the __name__ == ' __main__ ' : 
    P1 = Process (target = func1, args = ( ' parameter ' ,)) 
    p1.start () 
    Print ( ' hahahahha ' )
     # perceive the end of a child process will become asynchronous synchronization: before you join asynchronous 
    p1.join ()
     # after the join is synchronized 
    Print ( ' qqqqqqqqq ' )

result:

 

Practice: We want to achieve output of 10 words asynchronous, synchronous final output of finished.

from multiprocessing import Process

def func1(args):
    print('*'*args)

if __name__ == '__main__':
    for i in range(10):
        p1 = Process(target=func1,args=(i,))
        p1.start()
    p1.join()
    print('执行完毕！')

But we found, "finished" words always follow printout behind the longest sentence, 10 but because of the above sentence is asynchronous, the longest sentence is not always the final output, so we this can not realistically our needs.

from multiprocessing import Process

def func1(args):
    print('*'*args)

if __name__ == '__main__':
    p_list = [] #创建一个空列表用来存放等会生产的进程对象
    for i in range(10):
        p1 = Process(target=func1,args=(i,))
        p_list.append(p1)#将每个进程对象依次存放进列表中
        p1.start()
    [i.join() for i in p_list]  # 运用列表推导式：循环列表，依次对列表中的进程对象执行join()方法。之前所有进程必须在这里执行完才能执行下面的代码。
    print('执行完毕！')

结果1：　　结果2：