[Python-ideas] Replacing the standard IO streams (was Re: changing sys.stdout encoding)

[Stephen J. Turnbull]

^^^^^^^[[[[[[[[[@[@Nick Coghlan writes:
 > On Mon, Jun 11, 2012 at 12:34 AM, Serhiy Storchaka <storchaka at gmail.com> wrote:

 > > open(sys.stdin.fileno()) is not guaranteed to work if the input or output
 > > have occurred before.
[...]

 > Right, but the point of this discussion is to document the cleanest
 > available way for an application to change these settings at
 > *application start* (e.g. to support an "--encoding" parameter). Yes,
 > there are potential issues if you use any of these mechanisms while
 > there is data in the buffers,

+1

The OP's problem is a real one.  His use case (the "--encoding"
parameter) seems to be the most likely one in production use, so the
loss of buffered data issue should rarely come up.  Changing encodings
on the fly offers plenty of ways to lose data besides incomplete
buffers, anyway.

I am a little concerned with MRAB's report that

    import sys
    print("hello")
    sys.stdout.flush()
    sys.stdout = open(sys.stdout.fileno(), 'w', encoding='utf-8')
    print("hello")

doesn't work as expected, though.  (It does work for me on Mac OS X,
both as above -- of course there are no '\r's in the output -- and
with 'print("hello", end="\r\n")'.)