(vii) More than 7-5 processes

The difference between multi-process and multithreading
Multithreading uses a core of the CPU and is suitable for IO-intensive
Multi-process uses multiple cores of the CPU and is suitable for operation-intensive

Component
Python offers very good multi-process packages such as: multiprocessing
Multiprocessing supports the Forbidden City, communicates, shares data, performs different forms of synchronization, and provides components such as Processpipe,lock

Common methods of multiprocessing

# Multiprocessing.active_children ()   lists the existing child processes # Cpu_count ()                           Statistics CPU Number example: Import  MULTIPROCESSINGP = Multiprocessing.cpu_count () m = Multiprocessing.active_children () print  pprint m run Result: 4[]

　　

Process
1. Create a Process object
p = multiprocessing. Process (Target=worker, args= (5,))
Note: target= function name
The parameters required by the args= function are passed in as a tuple
2. Process Common methods
Is_alive () Determine if the process exists
Run () Start process
Start () starts the process and automatically calls the Run method
Join (timeout) waits for the process to end or time out
3. Process Common Properties
Name process names
The PID of PID process
Example:

Import  multiprocessingimport  timedef Worker (interval):    time.sleep (interval)    print "Hell World!!!" if __name__ = = "__main__":    p = multiprocessing. Process (Target=worker, args= (5,))    P.start ()    print p.pid    print p.is_alive ()    p.join ()    # P.join ( timeout=3)     #等待紫禁城执行完毕或者超时退出    print "End main"    print p.name    print P.pid

Operation Result:

17348Truehell World!!! End mainProcess-117348

Multi-Process instances:

Import  timefrom datetime import  datetimeimport  multiprocessingnow = Datetime.strftime (DateTime.Now (), " %y-%m-%d%h:%m:%s ") def worker (Name,interval):    start = Datetime.strftime (DateTime.Now (),"%y-%m-%d%h:%m:%s ")    print "{0} start {1}". Format (Name,start)    time.sleep (interval)    end = Datetime.strftime (DateTime.Now (), " %y-%m-%d%h:%m:%s ")    print" {0} end  {1} ". Format (name,end) If __name__ = =" __main__ ":    print" main start "    print  "This  computer has {0} CPU". Format (Multiprocessing.cpu_count ())    P1 = multiprocessing. Process (target=worker,args= ("Worker1", 2))    P2 = multiprocessing. Process (target=worker,args= ("Worker2", 3))    p3 = multiprocessing. Process (target=worker,args= ("Worker3", 4))    P1.start ()    P2.start ()    p3.start ()    print  Multiprocessing.cpu_count () for    p in Multiprocessing.active_children ():        print "This pid of {0} is {1}". Format (p.name,p.pid)    Print  "main End"

Operation Result:

Main Startthis  computer have 4 cpu4this pid of Process-1 is 19872this pid of Process-3 are 19008this pid of Process-2 is 18844main End worker1 start 2017-12-08 23:40:12 worker2 start 2017-12-08 23:40:12 worker3 start 2017-12-08 23:40:12 Worke R1 End  2017-12-08 23:40:14 worker2 end  2017-12-08 23:40:15 Worker3 end  2017-12-08 23:40:16

　　

(vii) More than 7-5 processes