在python中读取stdin时,管道文件描述符错误

this

scriptA.py | scriptB.py

sys.stdout.write( "hello" )

print sys.stdin.read()

c:\> scriptA.py | scriptB.py
close failed: [Errno 22] Invalid argument
Traceback (most recent call last):
  File "c:\scriptB.py", line 20, in <module>
    print sys.stdin.read()
IOError: [Errno 9] Bad file descriptor

“关闭失败”消息似乎来自scriptA.py的执行。

发生了什么?