print('All subprocesses done.')
#3、子进程，用于调用一个外部进程(例如一条命令)，需要控制子进程的输入和输出
import subprocess
print('$ nslookup www.python.org')
r = subprocess.call(['nslookup', 'www.python.org'])
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'
) #相当于在命令行执行命令nslookup，然后手动输入：set q=mx python.org exit
print(output.decode('utf-8'))
print('Exit code:', p.returncode)
#4、进程间通信，Python的multiprocessing模块包装了底层的机制，提供了Queue、Pipes等多种方式来交换数据。由于Windows没有fork调用，因此，multiprocessing需要“模拟”出fork的效果，父进程所有Python对象都必须通过pickle序列化再传到子进程去
from multiprocessing import Process, Queue
import os, time, random
def write(q): #写数据进程执行的代码:
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())
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)
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.')
#控制进程的输入与输出
import subprocess
print('$ nslookup www.python.org')
r = subprocess.call(['nslookup', 'www.python.org'])
print('Exit code', r)
#子进程还需要输入
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
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 % from queue.' % value)
if __name__ == '__main__':
#父进程创建Queue,并传递给各个子进程
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()
return 'done {0}'.format(name)
if __name__ == '__main__':
print('Parent process {0} is running'.format(os.getpid()))
p = Pool(4)
result = []
for i in range(5):
result.append(p.apply_async(long_time_task, (i, )))
print('Waiting for all subprocesses done...')
p.close()
p.join()
print('All subprocesses done')
# print(result)
for res in result:
print(res.get())
import subprocess
print('nslookup www.python.org')
res = subprocess.call(['nslookup', 'www.python.org'])
print('Exit code:{0}'.format(res))
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 {0}'.format(p.returncode))
end = time.time()
print('Task {0} {1:.2} seconds'.format(name, end-start))
return 'done {0}'.format(name)
if __name__ == '__main__':
print('Parent process {0} is running'.format(os.getpid()))
p = Pool(4)
result = []
for i in range(5):
result.append(p.apply_async(long_time_task, (i,)))
print('Waiting for all subprocesses done...')
p.close()
p.join()
print('All subprocesses done')
# print(result)
for res in result:
print(res.get())
import subprocess
print('nslookup www.python.org')
res = subprocess.call(['nslookup','www.python.org'])
print('Exit code:{0}'.format(res))
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 {0}'.format(p.returncode))
