创建子进程
目录:https://blog.csdn.net/qq_30923243/article/details/83505907
# coding:utf-8
from multiprocessing import Process
import os
#子进程要执行的代码
def run_proc(name):
print('Run child process %s(%s)...' % (name, os.getpid()))
if __name__ == '__main__':
. print('Parent process %s.' % os.getpid())
p = Process(target = run_proc, args=('test',)) #子进程执行函数run_proc 子进程名字test 创建子进程
print('Child process will start.')
p.start() # 启动子进程
p.join() # 方法可以等待子进程结束后再继续往下运行,通常用于进程间的同步。
print('child process end')
批量创建子进程
from multiprocessing import Pool
import os, time, random
def long_time_task(name):
print('Run task %s (%s)...' % (name, os.getpid()))
start = time.time()
time.sleep(random.random() * 3)
end = time.time()
print('Task %s runs %0.2f seconds.' % (name, (end - start)))
if __name__=='__main__':
print('Parent process %s.' % os.getpid())
p = Pool(3) #pool默认大小是CPU核数
for i in range(5):
p.apply_async(long_time_task, args=(i,))
print('Waiting for all subprocesses done...')
p.close()
p.join()
print('All subprocesses done.')
输出:
Parent process 43936. #父进程
Waiting for all subprocesses done...
Run task 0 (43816)... #开始创建3个子进程
Run task 1 (40776)...
Run task 2 (39044)...
Task 0 runs 0.43 seconds. # 子进程0结束
Run task 3 (43816)... # 子进程3创建,当前pool内共有3个子进程
Task 1 runs 1.15 seconds. # 子进程1结束
Run task 4 (40776)... # 子进程4创建,当前pool内共有3个子进程
Task 3 runs 0.82 seconds. # 剩下的子进程执行结束
Task 4 runs 0.91 seconds.
Task 2 runs 2.12 seconds.
All subprocesses done.
进程间通信
进程间通信是通过Queue、Pipes等实现的。
# coding:utf-8
from multiprocessing import Process, Queue
import os, time, random
def write(q):
for value in ['A', 'B', 'C']:
print('put %s to queue' % value)
q.put(value)
time.sleep(random.random())
def read(q):
while True:
value = q.get(True)
print('Get %s from queue.' % value)
if __name__=='__main__':
# 父进程创建Queue,并传给各个子进程:
q = Queue()
pw = Process(target=write, args=(q,))
pr = Process(target=read, args=(q,))
# 启动子进程pw,写入:
pw.start()
# 启动子进程pr,读取:
pr.start()
# 等待pw结束:
pw.join()
# pr进程里是死循环,无法等待其结束,只能强行终止:
pr.terminate()