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As others mentioned, the question is not Python-specific. When a process is spawned, it's the parent's duty to set the child's file descriptors (or to allow them to be inherited).

正如其他人提到的那样，问题不是特定于Python的。当一个进程产生时，父进程必须设置子进程的文件描述符（或允许它们被继承）。

So, this is not even OS-specific, but actually application specific. For example, you might have a different anser for Gnome and KDE. Or when executing the file from within Windows Explorer or 7-Zip (I think; I know how this works on Unix, not so sure on Windows). Different applications spawning the process might be making different arrangements.

因此，这甚至不是特定于操作系统的，而是实际上特定于应用程序。例如，您可能对Gnome和KDE使用不同的anser。或者在Windows资源管理器或7-Zip中执行文件时（我想;我知道这在Unix上是如何工作的，在Windows上不太确定）。产生该过程的不同应用可能会做出不同的安排。

On Linux, you can find out by running lsof on the python process, which will list the opened files and tell you where exactly your stdout is going. Here's your code, changed to do just that:

在Linux上，您可以通过在python进程上运行lsof来找到它，它将列出打开的文件并告诉您stdout的确切位置。这是你的代码，改为做到这一点：

#!/usr/bin/env python

# vi: ai sts=4 sw=4 et

import sys, os, pprint
import subprocess

f = open("/tmp/output.txt", "w")

for stream in (sys.stdout, sys.stdin, sys.stderr):
    print (stream, file=f)
    print ("STTY?", stream.isatty(), file=f)
    print ("fileno:", stream.fileno(), file=f)
    print ("name:", stream.name, file=f)

#    print (pprint.pprint(dir(stream)), file=f)
    print (file=f)

subprocess.call ("lsof -p %s" % os.getpid(), stdout = f, shell = True)

Only the last line is actually important. See the output for a normal run:

只有最后一行才是实际重要的。查看正常运行的输出：

(...)
test.py 29722 xxx    0u   CHR  136,4      0t0      7 /dev/pts/4
test.py 29722 xxx    1u   CHR  136,4      0t0      7 /dev/pts/4
test.py 29722 xxx    2u   CHR  136,4      0t0      7 /dev/pts/4

And when redirecting the output to a file:

将输出重定向到文件时：

(...)
test.py 29728 xxx    0u   CHR  136,4      0t0       7 /dev/pts/4
test.py 29728 xxx    1w   REG   0,38        0 2070222 /tmp/asdf.txt
test.py 29728 xxx    2u   CHR  136,4      0t0       7 /dev/pts/4

See that the file #1 has changed? Same will happen when you run it from Unity, telling you where that is going.

看到文件＃1已更改？当你从Unity运行它时会发生同样的事情，告诉你它在哪里。

I didn't exactly reproduce your problem, as my Gnome 3 file manager won't run scripts like that and I'd not look into it, but I'm curious to know where yours goes.

我没有完全重现你的问题，因为我的Gnome 3文件管理器不会运行这样的脚本而且我不会调查它，但我很想知道你的去向。