Python3多进程与多线程区别及使用（1.进程）

1 multiprocessing.Process(group=None, target=None, name=None, args=(), kwargs={}, *, daemon=None)

import multiprocessing
import os


def run_proc(name):
    print(‘Child process {0} {1} Running ‘.format(name, os.getpid()))


if __name__ == ‘__main__‘:
    print(‘Parent process {0} is Running‘.format(os.getpid()))
    for i in range(5):
        p = multiprocessing.Process(target=run_proc, args=(str(i),))
        print(‘process start‘)
        p.start()
    p.join()
    print(‘Process close‘)



结果：
Parent process 5408 is Running
process start
process start
process start
process start
process start
Child process 0 1044 Running 
Child process 1 1120 Running 
Child process 3 10824 Running 
Child process 2 9292 Running 
Child process 4 10528 Running 

import multiprocessing
import os
import time
def run_task(name):
  print(‘Task {0} pid {1} is running, parent id is {2}‘.format(name, os.getpid(), os.getppid()))
  time.sleep(1)
  print(‘Task {0} end.‘.format(name))
if __name__ == ‘__main__‘:
  print(‘current process {0}‘.format(os.getpid()))
  #设定池内进程数
  p = multiprocessing.Pool(processes=3)
  for i in range(6):
    p.apply_async(run_task, args=(i,))
  print(‘Waiting for all subprocesses done...‘)
  p.close()
  p.join()
  print(‘All processes done!‘) 

current process 562
Task 0 pid 778 is running, parent id is 562
Task 1 pid 779 is running, parent id is 562
Task 2 pid 780 is running, parent id is 562
Waiting for all subprocesses done...
Task 1 end.
Task 0 end.
Task 2 end.
Task 3 pid 779 is running, parent id is 562
Task 4 pid 778 is running, parent id is 562
Task 5 pid 780 is running, parent id is 562
Task 4 end.
Task 5 end.
Task 3 end.
All processes done!

apply(func[,args[,kwds]]))

import multiprocessing
import os
import time
def run_task(name):
  print(‘Task {0} pid {1} is running, parent id is {2}‘.format(name, os.getpid(), os.getppid()))
  time.sleep(1)
  print(‘Task {0} end.‘.format(name))
if __name__ == ‘__main__‘:
  print(‘current process {0}‘.format(os.getpid()))
  p = multiprocessing.Pool(processes=3)
  for i in range(6):
    p.apply(run_task, args=(i,))
  print(‘Waiting for all subprocesses done...‘)
  p.close()
  p.join()
  print(‘All processes done!‘)

current process 562
Task 0 pid 785 is running, parent id is 562
Task 0 end.
Task 1 pid 786 is running, parent id is 562
Task 1 end.
Task 2 pid 787 is running, parent id is 562
Task 2 end.
Task 3 pid 785 is running, parent id is 562
Task 3 end.
Task 4 pid 786 is running, parent id is 562
Task 4 end.
Task 5 pid 787 is running, parent id is 562
Task 5 end.
Waiting for all subprocesses done...
All processes done!

from multiprocessing import Process, Queue
import os, time, random
# 写数据进程执行的代码:
def proc_write(q,urls):
  print(‘Process(%s) is writing...‘ % os.getpid())
  for url in urls:
    q.put(url)
    print(‘Put %s to queue...‘ % url)
    time.sleep(random.random())
# 读数据进程执行的代码:
def proc_read(q):
  print(‘Process(%s) is reading...‘ % os.getpid())
  while True:
    url = q.get(True)
    print(‘Get %s from queue.‘ % url)
if __name__==‘__main__‘:
  # 父进程创建Queue，并传给各个子进程：
  q = Queue()
  proc_writer1 = Process(target=proc_write, args=(q,[‘url_1‘, ‘url_2‘, ‘url_3‘]))
  proc_writer2 = Process(target=proc_write, args=(q,[‘url_4‘,‘url_5‘,‘url_6‘]))
  proc_reader = Process(target=proc_read, args=(q,))
  # 启动子进程proc_writer，写入:
  proc_writer1.start()
  proc_writer2.start()
  # 启动子进程proc_reader，读取:
  proc_reader.start()
  # 等待proc_writer结束:
  proc_writer1.join()
  proc_writer2.join()
  # proc_reader进程里是死循环，无法等待其结束，只能强行终止:
  proc_reader.terminate()

multiprocessing.Pipe([duplex])

from multiprocessing import Process, Pipe
def send(pipe):
  pipe.send([‘spam‘,42, ‘egg‘])  # send 传输一个列表
  pipe.close()
if __name__ == ‘__main__‘:
  (con1, con2) = Pipe()              # 创建两个 Pipe 实例
  sender = Process(target=send, args=(con1, ))   # 函数的参数，args 一定是实例化之后的 Pip 变量，不能直接写 args=(Pip(),)
  sender.start()                  # Process 类启动进程
  print("con2 got: %s" % con2.recv())       # 管道的另一端 con2 从send收到消息
  con2.close()   

con2 got: [‘spam‘, 42, ‘egg‘]

from multiprocessing import Process, Pipe


def talk(pipe):
    pipe.send(dict(name=‘Bob‘, spam=42))  # 传输一个字典
    reply = pipe.recv()  # 接收传输的数据
    print(‘talker got:‘, reply)


if __name__ == ‘__main__‘:
    (parentEnd, childEnd) = Pipe()  # 创建两个 Pipe() 实例，也可以改成 conf1， conf2
    child = Process(target=talk, args=(childEnd,))  # 创建一个 Process 进程，名称为 child
    child.start()  # 启动进程
    print(‘parent got:‘, parentEnd.recv())  # parentEnd 是一个 Pip() 管道，可以接收 child Process 进程传输的数据
    parentEnd.send({x * 2 for x in ‘spam‘})  # parentEnd 是一个 Pip() 管道，可以使用 send 方法来传输数据
    child.join()  # 传输的数据被 talk 函数内的 pip 管道接收，并赋值给 reply
    print(‘parent exit‘)

parent got: {‘name‘: ‘Bob‘, ‘spam‘: 42}
talker got: {‘pp‘, ‘mm‘, ‘aa‘, ‘ss‘}
parent exit