[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[Matthias St.Pierre]

New submission from Matthias St.Pierre:

raw_input yields trailing carriage return ('\r') when C:\Python27\python.exe is 
called using the -u option

How to reproduce the error: save the attached file 'input.py' which contains 
the following lines

-- begin input.py --

i = raw_input("enter y or n: ")
print(repr(i))
print([ord(c) for c in i])

-- end input.py --

then run the two following commands from a windows command shell
python input.py
python -u input.py
and compare the output. (see transcript 1 below)

The same bug affects also the interactive mode: start 'python -u' and enter an 
arbitrary command. You will get a syntax error at the end of line. (see 
transcript 2 below)


-- begin transcript 1 of cmd session --

C:\Temp>where python
C:\Python27\python.exe

C:\Temp>python --version
Python 2.7.8

C:\Temp>type input.py

i = raw_input("enter y or n: ")
print(repr(i))
print([ord(c) for c in i])

C:\Temp>python input.py
enter y or n: y
'y'
[121]
-- end transcript 1 of cmd session --


-- begin transcript 2 of cmd session --

C:\Temp>python -u input.py
enter y or n: y
'y\r'
[121, 13]

C:\Temp>python -u
Python 2.7.8 (default, Jun 30 2014, 16:08:48) [MSC v.1500 64 bit (AMD64)] on 
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print "hello world"
  File "", line 1
print "hello world"
   ^
SyntaxError: invalid syntax
>>>

-- end transcript 2 of cmd session --

--
components: Interpreter Core, Windows
files: input.py
messages: 222613
nosy: msp
priority: normal
severity: normal
status: open
title: 'python -u' yields trailing carriage return '\r'  (Python2 for Windows)
type: behavior
versions: Python 2.7
Added file: http://bugs.python.org/file35913/input.py

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[Matthias St.Pierre]

Matthias St.Pierre added the comment:

correction: the markers for transcripts 1 and 2 were inserted at the wrong 
location; here's the correction:


-- begin transcript 1 of cmd session --

C:\Temp>where python
C:\Python27\python.exe

C:\Temp>python --version
Python 2.7.8

C:\Temp>type input.py

i = raw_input("enter y or n: ")
print(repr(i))
print([ord(c) for c in i])

C:\Temp>python input.py
enter y or n: y
'y'
[121]

C:\Temp>python -u input.py
enter y or n: y
'y\r'
[121, 13]


-- end transcript 1 of cmd session --


-- begin transcript 2 of cmd session --

C:\Temp>python -u
Python 2.7.8 (default, Jun 30 2014, 16:08:48) [MSC v.1500 64 bit (AMD64)] on 
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print "hello world"
  File "", line 1
print "hello world"
   ^
SyntaxError: invalid syntax
>>>

-- end transcript 2 of cmd session --

--

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[Ezio Melotti]

Changes by Ezio Melotti :


--
nosy: +haypo

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[R. David Murray]

R. David Murray added the comment:

This is the documented behavior of the -u option.  It puts the streams in 
binary mode "on systems where it matters", which would be windows.  That is, 
universal newline processing is disabled when you use -u.

Note that this is no longer an issue in python3: there, -u only affects 
buffering, and not the binary/text mode (because in python3 there is always a 
distinction between binary and text mode, regardless of platform).

--
nosy: +r.david.murray
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[STINNER Victor]

STINNER Victor added the comment:

The bug is not on print, but raw_input().

In Python 3, I worked on the following issues to support fully binary standard 
streams:

 - #10841: "binary stdio"
 - #11272: "input() has trailing carriage return on windows", fixed in Python 
3.2.1
 - #11395: "print(s) fails on Windows with long strings", fixed in Python 3.2.1
 - #13119: "Newline for print() is \n on Windows, and not \r\n as expected", 
will be fixed in Python 3.2.4 and 3.3 (not released yet)

It looks like this issue is the same than #11272: input() removes '\n' but not 
'\r'.

--
resolution: not a bug -> 
status: closed -> open

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[STINNER Victor]

STINNER Victor added the comment:

I backported and adapted most Python 3 fixes related to the Windows binary mode 
for stdout/stderr used when Python is started with the -u command line option. 
See attached binary.patch.

My change to file.write() looks wrong because the function returns None and 
does not loop until all bytes are written.

By the way, string_write() doesn't check if fwrite(n) wrote less than n bytes 
or failed with an error.

See also the issue #21090 which improves error handling in the file object.

--
keywords: +patch
Added file: http://bugs.python.org/file36145/binary.patch

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[STINNER Victor]

STINNER Victor added the comment:

While testing binary.patch, test_subprocess failed because of the issue #19612. 
I backported the fix:

changeset:   91905:039ac3f01c4e
branch:  2.7
parent:  91895:bffa0b8a16e8
user:Victor Stinner 
date:Tue Jul 29 00:04:54 2014 +0200
files:   Lib/subprocess.py Misc/NEWS
description:
Issue #19612: subprocess.communicate() now also ignores EINVAL when using at
least two pipes.

--

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[issue21946] 'python -u' yields trailing carriage return '\r' (Python2 for Windows)

[Zachary Ware]

Zachary Ware  added the comment:

It's not entirely clear from a quick read whether this was actually fixed or 
not (probably?), but as 2.7 is out of support it no longer matters :)

--
nosy: +zach.ware
resolution:  -> out of date
status: open -> closed

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