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

Victor Stinner victor.stinner at gmail.com
Tue Jun 12 23:44:00 CEST 2012

sys.stdin = open(sys.stdin.fileno(), 'r',) sys.stdout = open(sys.stdout.fileno(), 'w',) sys.stderr = open(sys.stderr.fileno(), 'w',)

 sys.stdin = io.TextIOWrapper(sys.stdin.detach(), )  sys.stdout = io.TextIOWrapper(sys.stdout.detach(), )  ... None of these methods are not guaranteed to work if the input or output have occurred before.

You should set the newline option for sys.std* files. Python 3 does something like this:

if os.name == "win32:

translate "\r\n" to "\n" for sys.stdin on Windows

newline = None else: newline = "\n" sys.stdin = io.TextIOWrapper(sys.stdin.detach(), newline=newline, ) sys.stdout = io.TextIOWrapper(sys.stdout.detach(), newline="\n", ) sys.stderr = io.TextIOWrapper(sys.stderr.detach(), newline="\n", )

--

Lib/test/regrtest.py uses the following code which is not exactly correct (it creates a new buffered writer instead of reusing sys.stdout buffered writer):

def replace_stdout(): """Set stdout encoder error handler to backslashreplace (as stderr error handler) to avoid UnicodeEncodeError when printing a traceback""" import atexit

stdout = sys.stdout
sys.stdout = open(stdout.fileno(), 'w',
    encoding=stdout.encoding,
    errors="backslashreplace",
    closefd=False,
    newline='\n')

def restore_stdout():
    sys.stdout.close()
    sys.stdout = stdout
atexit.register(restore_stdout)

Victor

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