Windows上Python讀取stdin出錯

Windows上Python讀取stdin出錯

（金慶的專欄）

一段簡單的代碼，讀取stdin, 替換輸出到stdout:

#!/usr/bin/env python
import os, sys
input_file = sys.stdin
output_file = sys.stdout
for s in input_file:
    output_file.write(s.replace("abc", "def"))

代碼改自CookBook的    
Recipe 2.3. Searching and Replacing Text in a File

在Linux上運行正常：
$ cat input.txt | ./replace.py
 
但是在Windows的Dos視窗運行會報錯：
> type input.txt | replace.py
Traceback...
    for s in input_file:
IOError: [Errno 9] Bad file descriptor

如果用python調用就正常：
> type input.txt | python replace.py

原因是cmd.exe通過尾碼關聯運行py檔案存在問題。
詳見：Bad pipe filedescriptor when reading from stdin in python
http://stackoverflow.com/questions/1057638/bad-pipe-filedescriptor-when-reading-from-stdin-in-python

It seems that stdin/stdout redirect does not work when starting from a file association. This is not specific to python, but a problem caused by win32 cmd.exe.