[Python-ideas] Redesign of Python stdio backend

[drekin]

I would expect that all standard IO in Python goes through sys.stdin,
sys.stdout and sys.stderr or the underlying buffer or raw objects. The only
exception should be error messages before the sys.std* objects are
initialized.

I was surprised that this is actually not the case – reading input in the
interactive loop actually doesn't use sys.stdin (see
http://bugs.python.org/issue17620). However it uses its encoding, which
doesn't make sense. My knowledge of the actual implementation is rather
poor, but I got impression that the codepath of getting input from user in
interactive loop is complicated. I would think that it consits just of
wrapping an underlying system call (or GNU readline or anything) in
sys.stdin.buffer.raw.readinto or something. With current implementation,
fixing issues may be complicated – for example handling SIGINT produced by
Ctrl-C on Windows issues. There is a closed issue
http://bugs.python.org/issue17619 but also an open issue
http://bugs.python.org/issue18597.

There is also a seven years old issue http://bugs.python.org/issue1602
regarding Unicode support on Windows console. Even if the issue isn't
fixed, anyone could just write their own sys.std* objects a install them in
the running interpreter. This doesn't work now because of the problem
described.

I just wanted to bring up the idea of redesign the stdio backend which also
results in fixing http://bugs.python.org/issue17620 and helping fixing the
others.

Regards, Drekin
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