# 多进程
# 创建子进程
'''
import os
print('Process (%s) start...' % os.getpid())
pid = os.fork()
if pid == 0:
print('%s %s' % (os.getpid(), os.getppid()))
else:
print('%s %s' % (os.getpid(), pid))
'''
# 启动一个子进程并等待结束
'''
import os
from multiprocessing import Process
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',))
print('Child process will start')
p.start()
p.join() # 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.')
'''
# Pool进程池，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(4) # 默认大小是CPU的核数
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.')
'''
# 子进程
# import subprocess
'''
print('$ nslookup www.python.org')
r = subprocess.call(['nslookup', 'www.liaoxuefeng.com'])
print('Exit code:', r)
'''
'''
print('$ nslookup')
p = subprocess.Popen(['nslookup'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
output, err = p.communicate(b'set q=mx\npython.org\nexit\n')
print(output.decode('utf-8'))
print('Exit code:', p.returncode)
'''
# 进程间通信 Queue,Pipes
from multiprocessing import Process, Queue
import os, time, random
# 写数据进程执行的代码
def write(q):
print('Process to write: %s' % os.getpid())
for value in ['A', 'B', 'C']:
print('Put %s to queue...' % value)
q.put(value)
time.sleep(random.random())
# 读数据进程执行的代码
def read(q):
print('Process to read: %s' % os.getpid())
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，无法等待结束，只能强行终止
pr.terminate()
