def child(wpipe):
    print('hello from child', os.getpid())
    while True:
        msg = 'how are you\n'.encode()
        os.write(wpipe, msg)
        time.sleep(1)

def parent():
    rpipe, wpipe = os.pipe()
    pid = os.fork()
    if pid == 0:
        child(wpipe)
        assert False, 'fork child process error!'
    else:
        os.close(wpipe)
        print('hello from parent', os.getpid(), pid)
        fobj = os.fdopen(rpipe, 'r')
        while True:
            recv = os.read(rpipe, 32)
            print recv

parent()

how are you

how are you

how are you

def child(wpipe):
    print('hello from child', os.getpid())
    while True:
        msg = 'how are you\n'.encode()
        os.write(wpipe, msg)
        time.sleep(1)

def parent():
    rpipe, wpipe = os.pipe()
    pid = os.fork()
    if pid == 0:
        os.close(rpipe)
        child(wpipe)
        assert False, 'fork child process error!'
    else:
        os.close(wpipe)
        print('hello from parent', os.getpid(), pid)
        fobj = os.fdopen(rpipe, 'r')
        while True:
            recv = fobj.readline()[:-1]
            print recv

parent()

def spawn(prog, *args):
    stdinFd = sys.stdin.fileno()
    stdoutFd = sys.stdout.fileno()

    parentStdin, childStdout = os.pipe()
    childStdin, parentStdout= os.pipe()

    pid = os.fork()
    if pid:
        os.close(childStdin)
        os.close(childStdout)
        os.dup2(parentStdin, stdinFd)#输入流绑定到管道,将输入重定向到管道一端parentStdin
        os.dup2(parentStdout, stdoutFd)#输出流绑定到管道,发送到子进程childStdin
    else:
        os.close(parentStdin)
        os.close(parentStdout)
        os.dup2(childStdin, stdinFd)#输入流绑定到管道
        os.dup2(childStdout, stdoutFd)
        args = (prog, ) + args
        os.execvp(prog, args)
        assert False, 'execvp failed!'

if __name__ == '__main__':
    mypid = os.getpid()
    spawn('python', 'pipetest.py', 'spam')

    print 'Hello 1 from parent', mypid #打印到输出流parentStdout, 经管道发送到子进程childStdin
    sys.stdout.flush()
    reply = raw_input()
    sys.stderr.write('Parent got: "%s"\n' % reply)#stderr没有绑定到管道上

    print 'Hello 2 from parent', mypid
    sys.stdout.flush()
    reply = sys.stdin.readline()#另外一种方式获得子进程返回信息
    sys.stderr.write('Parent got: "%s"\n' % reply[:-1])

mypid = os.getpid()
parentpid = os.getppid()
sys.stderr.write('child %d of %d got arg: "%s"\n' %(mypid, parentpid, sys.argv[1]))

for i in range(2):
    time.sleep(3)
    recv = raw_input()#从管道获取数据,来源于父经常stdout
    time.sleep(3)
    send = 'Child %d got: [%s]' % (mypid, recv)
    print(send)#stdout绑定到管道上,发送到父进程stdin
    sys.stdout.flush()