pythonw should set `sys.stdout` and `sys.stdin` to valid objects.

Bug report

Bug description:

So not exactly a bug -- but I wouldn't call it a feature request either, so I filed it as a bug.

The issue is that pythonw on Windows sets sys.stdout and sys.stdin to None.

This is problematic because while, e.g. print() will not fail, if not do anything useful, other things like warnings and logging, etc., may try to use stdout or stderr, and they will then fail.

See #107792 and #57791

So one might say: "don't do that" -- fair enough, except the user suffering from the problem may not be the one that wrote the code that's calling stderr -- it could be in a library, for instance. Library writers are often not thinking about windowed apps, and shouldn't have to do something special to accommodate them in any case.

See this note in the PyInstaller docs:

https://pyinstaller.org/en/stable/common-issues-and-pitfalls.html?highlight=os.devnull#sys-stdin-sys-stdout-and-sys-stderr-in-noconsole-windowed-applications-windows-only

In which the solution is:

import sys
import os

if sys.stdout is None:
    sys.stdout = open(os.devnull, "w")
if sys.stderr is None:
    sys.stderr = open(os.devnull, "w")

It's not unreasonable for library authors to expect that stdout and stderr to be valid.

So couldn't pythonw add that code by default? users could override it themselves, of course.

NOTE: tested recently on py3.12 -- but this has been an issue for quite some time.

NOTE2: this isn't an issue on the Mac, because its pythonw redirects to the system off-screen console.

CPython versions tested on:

3.12

Operating systems tested on:

Windows

首先在 Windows 上使用 pythonw 重現該行為，並查看 issue 中連結的討論以及 PyInstaller 關於缺少標準串流的文件。確定 pythonw 應如何提供有效的 sys.stdin 和 sys.stdout 物件，同時不破壞現有行為，然後驗證警告、logging 和與 print 相關的使用情境是否如預期運作。