无法在进程之间建立管道

Question

我正在尝试在父进程和子进程之间创建管道：

index()

此代码可以启动子进程，但firstsentence = input('Enter a sentence: ') firstsentence = firstsentence.lower() words = firstsentence.split(' ') s = "" for word in words: s += str(words.index(word)+1) + " " print(s) 阻止运行而没有任何结果。怎么了？

编辑子进程运行以下循环echo-program（＆＃34; echo.py＆＃34;）：

def launch_process():

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

    pid = os.fork()
    if pid:
        os.close(childStdout)
        os.close(childStdin)
        self.set_configuration()            
    else:
        os.close(parentStdout)
        os.close(parentStdin)
        os.dup2(childStdin, 0)
        os.dup2(childStdout, 1)            
        os.execvp("echo.py", "")
        raise RuntimeError

#after launch_process() call...
pipein = os.fdopen(parentStdin) #I saved both parentStdin and parentStdout variable as global
while True:
    time.sleep(3)
    os.write(parentStdout, ("command").encode())
    line = pipein.readline() #the program stops here
    print(line)