Terry J. Reedy added the comment:
I closed #24572 as a duplicate of this. It is the same issue except for
printing \r instead of \b. These issues are not about responses to keyboard
actions when entering text into an Idle editor window. During entry, just
about any cntl/alt/function/shift/key combination can be intercepted to and
translated to arbitrary action. They are also not about REPL echo. For 3.4+
Win7, both console Python and Shell echo '\b\t\x08\x09' as '\x08\t\x08\t'.
Carol's report suggest that the same is true on Mac also.
Both issues *are* about print(s, file=outfile), where s is the result of
processing all args except 'file' and outfile defaults to sys.stdout. The print
call is the same as outfile.write(s), so outfile (and sys.stdout) could be any
object with a write method.
>>> print('hello\b\b\b\b\bHELLO')
helloHELLO
>>> import sys; sys.stdout.write('hello\b\b\b\b\bHELLO'+'\n')
helloHELLO
(I actually see the same circles as Al, but copy-paste does not seem to work as
well for me.)
So both issues are about the effect of writing 'control chars', in particular
\b and \r, to a file. Well, that depends on the file. Some possibilities are
copy as is (StringIO), encode and copy (disk file, socket), ignore, display as
one glyph, display as multiple chars, non-destructively backspace (like
backspace on typewriters and printing terminals and left-arrow elsewhere), or
destructively backspace (like backspace on as most (all?) screen keyboards).
After non-destructive movement of the 'cursor' position, the possibilities for
following graphical chars are overwrite (like typewriters), replace, and insert
(the modes sometimes selected by the Insert key). Non-destructive backspace
followed by overwrite (meaning 'HELLO' printed on top of 'hello') is the
original meaning of 'backspace'.
Having said all this, I am sympathetic to the idea that there should be an
option to have 'print(ascii_string)' in user code give the same result in the
console and Idle. I think this would best be accomplished by a
least-common-denominator SimpleTerm subclass of tkinter.Text put somewhere in
the tkinter package. (This would be a new issue that should start on
python-ideas list.) However, I would consider something Idle specific.
Does the following work the same on *nix and Mac as Windows?
>>> print('hello\rHELLO')
HELLO # helloHELLO with Win7 Idle
Are there any control-chars (other than \n) that work might work in the
consoles on all three systems and that should be included?
Carol, another difference between the Windows console and Idle is that tk and
hence Idle support the entire BMP subset of unicode. This should also be
mentioned in the doc.
----------
stage: -> needs patch
type: -> enhancement
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Python tracker <[email protected]>
<http://bugs.python.org/issue23220>
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